Write back (5)
I believe the answer is:
reply
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">write back</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 reply that I've seen before include "Counter" , "Come back" , "Answer, respond" , "Return" , "Reciprocate" .)