Cold joint is something to eat (4)
I believe the answer is:
chip
'something to eat' is the definition.
(chip is a kind of food)
'cold joint' is the wordplay.
'cold' becomes 'c' (eg on taps).
'joint' becomes 'hip' (hip is a kind of joint**).
'c'+'hip'='CHIP'
'is' is the link.
(Other definitions for chip that I've seen before include "one bit of fast food > counter" , "Golf shot; item of fried food" , "Piece of old block, potato, etc" , "Game counter representing money" , "Slice - approach shot in golf" .)