Such temperatures are cold to bear (5)
I believe the answer is:
polar
'bear' is the definition.
(polar bear is a kind of bear)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for polar that I've seen before include "Relating to the Arctic or Antarctic" , "Of the far north or south" , "Extremely cold region" , "Of the cold regions" , "extremes of 3 or 26 [NORTH OR SOUTH]" .)