Question: Alex Smith played for what  professional association football club based in Southend-on-Sea, Essex, England

Context paragraphs:
Wrexham A.F.C.: Wrexham Association Football Club (Welsh: "Clwb Pêl-droed Wrecsam" ) is a professional association football club based in Wrexham, Wales.  Based on the club's recorded formation date of 1864, they are the oldest club in Wales and the third oldest professional football team in the world.  Since August 2011 Wrexham have been a supporter-owned football club.  As of May 2015, the club has 4,129 adult members and joint owners.

List of Rochdale A.F.C. seasons: Rochdale Association Football Club is an English professional association football club based in the town of Rochdale in Greater Manchester.  The club plays in the Football League One, the third tier in the English football league system.  The club's colours are black and blue and they play their home games at Spotland Stadium, which has a capacity of 10,249.  Formed in 1907 and nicknamed "the Dale", they were accepted into the Football League in 1921.  Since then, the club has remained in the bottom two professional divisions of English Football.

Notts County F.C.: Notts County Football Club is a professional association football club based in the city of Nottingham, Nottinghamshire, England.  With records of games as early as 28 November 1862, Notts County is recognised as the oldest association football team in the world now playing at a professional level.  Between 1888–89 and 2013–14 they played a total of 4,756 Football League matches – more than any other English team.  The team plays in League Two, the fourth tier of the English football league system.  County play their home games at Meadow Lane in black and white striped shirts.

List of Sutton United F.C. seasons: Sutton United Football Club, a professional association football club based in Sutton in the London Borough of Sutton, England, was founded in 1898 as a merger between Sutton Guild Rovers and Sutton Association Football Clubs.  They were elected to play in the Athenian League for the 1921–22 season.  They won the Athenian League title on three occasions and were runners-up once.  After thirty-seven seasons in the Athenian League, they joined the Isthmian League (given the subtitle First Division in 1973 and then Premier Division in 1977).  The club spent twenty-three seasons in the league, during that spell they won the title twice, reached the fourth round of the 1969–70 FA Cup, and reached the 1981 FA Trophy Final losing 1–0 to Bishop's Stortford.  In 1986 they won the first promotion in their history as champions of the Isthmian League, moving up to the Football Conference.

List of Plymouth Argyle F.C. results by opponent: Plymouth Argyle Football Club are an English professional association football club based in Plymouth, Devon.  They compete in Football League Two as of the 2015–16 season, the fourth division of the English football league system.  The club was formed in 1886 as Argyle Football Club, a name which was retained until 1903 when the club became professional and were elected to the Southern Football League.  The club also entered English football's premier knockout competition, the Football Association Challenge Cup, for the first time that same year.  The club joined the Football League in 1920, and have competed there since then, achieving multiple league titles, promotions and relegations.

Colchester United F.C.: Colchester United Football Club is a professional association football club based in the town of Colchester, Essex, England.  The team competes in League Two, the fourth tier of the English football league system.

Southend Manor F.C.: Southend Manor Football Club is a football club based in Southend-on-Sea, Essex, England.  The club are currently members of the Essex Senior League and play at Southchurch Park.

Southend United F.C.: Southend United Football Club is a professional association football club based in Southend-on-Sea, Essex, England.  The team compete in League One, the third tier of English football.  Southend are known as "The Shrimpers", a reference to the area's maritime industry included as one of the quarterings on the club badge.

Sheffield United F.C.: Sheffield United Football Club is a professional association football club based in the city of Sheffield, South Yorkshire, England.  The team competes in the Championship, the second tier of English football.  The football club was formed in 1889 as an offshoot of Sheffield United Cricket Club, and are nicknamed The Blades due to Sheffield's history of steel production.  The club have played their home games at Bramall Lane since their formation in 1889.  Bramall Lane is currently an all-seater ground with a capacity of 32,702.

Alex Smith (footballer, born 1947): Alexander "Alex" Smith (born 11 May 1947) is a former professional footballer, who played for Ossett Albion, Bradford City, Huddersfield Town, Southend United, Colchester United and Halifax Town.

Supporting paragraphs: Alex Smith (footballer, born 1947) Southend United F.C.
Answer: Southend United Football Club