Violent demonstrator (6)
I believe the answer is:
rioter
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">violent demonstrator</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for rioter that I've seen before include "He is taking part in a public affray" , "He runs amok in public" , "One engaged in a violent disturbance of the peace" , "One of a violent crowd" , "He's running amok in the street" .)