Most enthusiastic (7)
I believe the answer is:
keenest
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">most enthusiastic</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for keenest that I've seen before include "Most anxious" , "most piercing" , "Most enthusiastic" , "Sharpest" , "Most eager and sharp" .)