Hit back (9)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">hit back</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 retaliate that I've seen before include "Get one's own back" , "settle accounts" , "Attack in return for attack" , "Strike back, counter" , "Hit back" .)