Polar feature (6)
I believe the answer is:
icecap
'polar feature' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for icecap that I've seen before include "Permanent frozen polar cover" , "Cold mass permanently covering the polar regions or mountain peaks" , "Feature of polar regions" , "Frozen topping" , "mass covering the top of Everest?" .)