Vendetta (4)
I believe the answer is:
feud
'vendetta' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for feud that I've seen before include "Bitter disagreement between families" , "Persistent strife" , "Prolonged fight between families, very Sicilian" , "Vendetta" , "Prolonged dispute" .)