Element of plumage . . . and a feature shared by every answer crossing this one (7)
I believe the answer is:
feather
(Other definitions for feather that I've seen before include "A white one denotes cowardice" , "Free hat (anag)" , "'Birds of a . . . . . . . flock together'" , "English plume (de ma tante?)" , "thing of little importance" .)