Violence by an unruly mob (4)
I believe the answer is:
riot
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">violence by an unruly mob</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for riot that I've seen before include "Crowd violence" , "Violent crowd disturbance" , "unrestrained revelry" , "A wild public affray" , "scream" .)