Painfully cold beer (6)
I believe the answer is:
bitter
This clue could be a double definition.
'painfully cold' is the first definition.
'bitter' can be an answer for 'cold' (similar in meaning). I'm not certain of the 'painfully' bit.
'beer' is the second definition.
(bitter is a type of beer)
Can you help me to learn more?
(Other definitions for bitter that I've seen before include "Sharp-tasting or resentful" , "Tart or resentful" , "Hard to accept" , "Resentful, being piercingly cold" , "Sour British beer?" .)