Investigate closely (5)
I believe the answer is:
probe
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">investigate closely</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 probe that I've seen before include "Poke into" , "Question or examine closely" , "Question or examine thoroughly" , "Examine searchingly" , "Explore, examine" .)