Keenly enthusiastic (4)
I believe the answer is:
avid
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">keenly enthusiastic</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 avid that I've seen before include "Mad for diva" , "Keenly enthusiastic" , "hungry" , "Showing active interest and enthusiasm" , "Keenly interested" .)