White part of a Santa costume (5)
I believe the answer is:
beard
'white part of a santa costume' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for beard that I've seen before include "Whiskers" , "Facial growth" , "Vandyke, perhaps" , "Facial feature" , "Oppose with effrontery" .)