Breach of the peace (6)
I believe the answer is:
affray
'breach of the peace' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for affray that I've seen before include "Breach of the peace by public rioting" , "Disturbance in public place" , "public brawl" , "Brawl, disturbance" , "A fight or riot in public" .)