Acuity (8)
I believe the answer is:
keenness
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">acuity</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that acuity can be written as keenness)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for keenness that I've seen before include "Fervour" , "Enthusiasm" , "Avidity" , "Penetrating quality" , "Eagerness" .)