Very cold — incisive (6)
I believe the answer is:
biting
This clue is a double definition.
'very cold' is the first definition.
'incisive' is the second definition.
(thesaurus)
(Other definitions for biting that I've seen before include "(Of wit) harsh, cruel" , "Mordant" , "Acerbic" , "Caustic or cutting - like teeth?" , "Sarcastic; very cold" .)