Clash of clans (4)
I believe the answer is:
feud
'clash of clans' 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 "Conflict" , "Piece of land once" , "quarrel without end" , "Lasting hostility between people or groups" , "Prolonged fight between families, very Sicilian" .)