Great enthusiasm or keenness (4)
I believe the answer is:
zeal
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">great enthusiasm</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >'<span class="explanation-format__original">keenness</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(zeal is a kind of keenness)</span><br/ ><br/ ></span>
(Other definitions for zeal that I've seen before include "Zest, ardour" , "Eagerness and devotion" , "Laze about with energy" , "Zing" , "Great eagerness" .)