Swabs (4)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">swabs</span>' is the definition.<br/ ><span class="explanation-format__explanation">('mop' can be a synonym of 'swab')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for mops that I've seen before include "Swabs, wipes up" , "They're used to clean floors" , "grimaces" .)