Primo (4)
(Other definitions for aces that I've seen before include "Ones or elevens in cards" , "Case of top cards" , "Tennis serves the receiver can't reach" , "Two will make deuce" , "wartime pilots?" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">primo</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 grade a that I've seen before include "Top quality or classification" , "Top quality in alphabetic designation" , "Best quality" .)