Clean with water (4)
I believe the answer is:
wash
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">clean with water</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for wash that I've seen before include "Clean with liquid" , "Clean; thin coat of paint" , "Scrub" , "Stand up" , "Clean with water" .)