Quick sharp reply (7)
I believe the answer is:
riposte
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">quick sharp reply</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 riposte that I've seen before include "Rejoinder" , "Snappy comeback" , "Reply, response" , "Repartee; quick thrust (fencing)" , "Counter-thrust" .)