Complex sentence: In 2004 Tennant played a lead role in the Big Finish audio play series "Dalek Empire III" as Galanar, a young man who is given an assignment to discover the secrets of the Daleks.
Split into simpler sentences: In 2004 Tennant played a lead role in the Big Finish audio play series "Dalek Empire III". He played the part of Galanar, a young man who is given an assignment to discover the secrets of the Daleks.