Swirl of water (4)
I believe the answer is:
eddy
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">swirl of 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 eddy that I've seen before include "Boy" , "Chap" , "Circle around" , "Rapid circular current" , "Whirl (in fluid)" .)