A stoat in winter (6)
I believe the answer is:
ermine
'a stoat in winter' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ermine that I've seen before include "special trimmings" , "garb for nobility" , "Expensive white fur" , "'Trimming on royal robes, say (6)'" , "White fur of weasel" .)