Vegetable, cold and difficult to chew (5)
I believe the answer is:
chard
'vegetable' is the definition.
(I know that Chard is a type of vegetable greens)
'cold and difficult to chew' is the wordplay.
'cold' becomes 'c' (eg on taps).
'and' means one lot of letters go next to another.
'difficult to chew' becomes 'hard' (as in hard food).
'c'+'hard'='CHARD'
(Other definitions for chard that I've seen before include "Vegetable; Somerset town" , "Vegetable with edible leaves and stalks" , "Beet with edible leaves and stalks" , "Seakale beet" , "Variety of beet with edible white leaf stalks" .)