Unfriendly or slippery (3)
I believe the answer is:
icy
This clue is a double definition.
'unfriendly' is the first definition.
(I've seen this before)
'slippery' is the second definition.
(I've seen this in another clue)
(Other definitions for icy that I've seen before include "Posing danger on the road" , "Very cold, unfriendly" , "Freezing and slippy" , "Glacial" , "frozen over!" .)