Sending by post (7)
I believe the answer is:
mailing
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sending by post</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for mailing that I've seen before include "Posting" , "Sending by post" , "Dispatch by post" , "Sending a message" .)