Family feud (8)
I believe the answer is:
vendetta
'family feud' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for vendetta that I've seen before include "Blood-feud between families" , "A prolonged feud, associated with Sicily" , "Sicilian blood feud" , "murderous campaign?" , "Unremitting battle" .)