Cold tough vegetable
I believe the answer is:
chard
'vegetable' is the definition.
(I know that Chard is a type of leafy vegetable)
'cold tough' is the wordplay.
'cold' becomes 'c' (eg on taps).
'tough' becomes 'hard' (associated in meaning).
'c'+'hard'='CHARD'
(Other definitions for chard that I've seen before include "Green vegetable" , "Leafy green" , "Vegetable; Somerset town" , "Type of beet" , "Leaf stalks from a kind of beet" .)