Story of the Forsytes, again (4)
I believe the answer is:
saga
'story' is the definition.
(a saga is a long story)
'of the forsytes again' is the wordplay.
'of' says the answer is hidden in the clue.
'SAGA' is hidden within 'forsytes again'.
(Other definitions for saga that I've seen before include "Long detailed story" , "Old story" , "Account of great heroism" , "Tale of heroes" , "Soap opera" .)