Clue: Seat: I offered support for member not returned PM (9,5)
Answer: ISLINGTON NORTH
Explanation: Definition: Seat
A charade of 'I' plus ('offered') SLING ('support *for member*') plus TON ('not returned') plus NORTH ('PM'; Lord NORTH was Prime Minister of Great Britain 1770-1782). The House of Commons seat of the definition is held by Jeremy ~~Corbin~~ *Corbyn*.