Cold, hard food (5)
I believe the answer is:
chard
'food' is the definition.
(chard is a kind of food)
'cold hard' is the wordplay.
'cold' becomes 'C' (eg on taps).
'c'+'hard'='CHARD'
(Other definitions for chard that I've seen before include "salad" , "Vegetable with edible leaves and stalks" , "A beet; sounds like burnt" , "Kind of (Swiss?) beet with edible leaves" , "Vegetable; Somerset town" .)