Strike back (9)
I believe the answer is:
retaliate
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">strike back</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for retaliate that I've seen before include "Give back blow for blow" , "Get one's own back" , "Strike back, counter" , "Make tit-for-tat attack" , "Hit back" .)