Winter weasel (6)
I believe the answer is:
ermine
'winter weasel' 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 "White fur of stoat" , "White fur of weasel" , "Warm white covering" , "special trimmings" , "Stoat in its winter coat" .)