Down-producing duck (5)
I believe the answer is:
eider
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">down-producing duck</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for eider that I've seen before include "Duck supplying down" , "Source of fine soft down" , "Variety of duck" , "Large sea duck" , "Downy sea duck" .)