Disturber of the peace (6)
I believe the answer is:
rioter
'disturber of the peace' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for rioter that I've seen before include "He's running amok in the street" , "Troublemaker involved in disturbing the peace" , "hooligan" , "Person engaged in disorder" , "One involved in civil unrest" .)