Massacre in family shack (9)
I believe the answer is:
bloodshed
'massacre' is the definition.
(I know that bloodshed is a type of massacre)
'family shack' is the wordplay.
'family' becomes 'blood' (blood can mean one's family).
'shack' becomes 'shed' (I've seen this in another clue).
'blood'+'shed'='BLOODSHED'
'in' acts as a link.
(Other definitions for bloodshed that I've seen before include "The killing or wounding of people, very gory" , "Carnage" , "Indiscriminate slaughter" .)