Attack violently (6)
I believe the answer is:
assail
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">attack violently</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for assail that I've seen before include "Attack, lash out" , "Set upon" , "Charge" , "Maybe mug" , "Go for" .)