More unfriendly (5)
I believe the answer is:
icier
'more unfriendly' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for icier that I've seen before include "increasingly frigid" , "Colder even than 31 Across" , "More slippery" , "rather cold" , "Even more frozen" .)