Vegetable, cold and tough (5)
I believe the answer is:
chard
'vegetable' is the definition.
(chard is a kind of vegetable)
'cold and tough' is the wordplay.
'cold' becomes 'c' (eg on taps).
'and' is a charade indicator (letters next to each other).
'tough' becomes 'hard' ('hard' is associated in meaning with 'tough').
'c'+'hard'='CHARD'
(Other definitions for chard that I've seen before include "Type of beet" , "A beet; sounds like burnt" , "salad" , "Variety of beet with edible white leaf stalks" , "Vegetable with edible leaves and stalks" .)