Read up on (5)
I believe the answer is:
study
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">read up on</span>' is the definition.<br/ ><span class="explanation-format__explanation">(to study something is to read up on it)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for study that I've seen before include "Analysis" , "Small office" , "Writing-room" , "Examine carefully" , "Den - learning" .)