Find by investigation (5)
I believe the answer is:
trace
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">find by investigation</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 trace that I've seen before include "description of some elements?" , "indicator" , "Locate by investigation" , "Element" , "Track down or make copy" .)