Plumage (8)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">plumage</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 feathers that I've seen before include "Bird insulation" , "Plumage, insulation for birds" , "Possibly down" , "Plumages" , "Aids to flight" .)