Part of a bird's plumage (7)
I believe the answer is:
feather
'part of a bird's plumage' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for feather that I've seen before include "manipulate oar" , "Part of a bird's plumage" , "'Birds of a . . . . . . . flock together'" , "Quill" , "Free hat (anag)" .)