Dig; research deeply (5)
I believe the answer is:
delve
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">dig</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I know that dig can be written as delve)</span><br/ ><br/ >'<span class="explanation-format__original">research deeply</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ ></span>
(Other definitions for delve that I've seen before include "Fish around" , "Search deeply for information" , "Dig - research deeply" , "Make painstaking enquiries (into something)" , "Burrow" .)