Mention one by one (9)
I believe the answer is:
enumerate
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">mention one by one</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 enumerate that I've seen before include "Specify individually" , "Count - list" , "Count or mention items one by one" , "List one by one" .)