Singles (4)
I believe the answer is:
ones
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">singles</span>' is the definition.<br/ ><span class="explanation-format__explanation">('one' can be a synonym of 'single')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for ones that I've seen before include "Singles" , "Singletons" , "Aces" , "Individuals" , "Units" .)