Family joining city massacre (9)
I believe the answer is:
bloodbath
'massacre' is the definition.
(I know that bloodbath is a type of massacre)
'family joining city' is the wordplay.
'family' becomes 'blood' (I've seen this in another clue).
'joining' is a charade indicator (letters next to each other).
'city' becomes 'bath' (English city).
'blood'+'bath'='BLOODBATH'
(Other definitions for bloodbath that I've seen before include "carnage" , "Massacre" .)