What might come from mash being cold? (6)
I believe the answer is:
bitter
This clue is a double definition.
'what might come from mash' is the first definition.
(mash is a mixture used in brewing)
'being cold?' is the second definition.
('bitter' can be similar in meaning to 'cold')
(Other definitions for bitter that I've seen before include "Kind of British beer" , "Resentful or angry through disappointment" , "English beer, sounds sour" , "Beer; not sweet" , "Acrimonious; beer" .)