Fish-eating duck (4)
I believe the answer is:
smew
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">fish-eating duck</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for smew that I've seen before include "Bird" , "Species of merganser" , "Sea duck" , "Diver" , "Small merganser" .)