Very cold and resentful (6)
I believe the answer is:
bitter
I believe this clue is a double definition.
'very cold' is the first definition.
(bitter informally can mean very cold)
'resentful' is the second definition.
(synonyms)
'and' acts as a link.
(Other definitions for bitter that I've seen before include "Unpalatable; a beer" , "Beer; not sweet" , "Sarcastic (words); very cold" , "Not sweet; very cold" , "Sour tasting, like English ale" .)