Mavens (4)
I believe the answer is:
aces
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">mavens</span>' is the definition.<br/ ><span class="explanation-format__explanation">('ace' can be a synonym of 'maven')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for aces that I've seen before include "wartime pilots?" , "excellent service" , "never come back" , "Champions" , "Expert fliers" .)