Reptile or cold bird? (4)
I believe the answer is:
croc
'reptile' is the definition.
(short for crocodile)
'cold bird?' is the wordplay.
'cold' becomes 'c' (eg on taps).
'bird?' becomes 'roc' (mythological bird of prey).
'c'+'roc'='CROC'
'or' acts as a link.
(Other definitions for croc that I've seen before include "Pot tailless" , "creature heard to be a vicious one" , "Fierce reptile" , "Short reptile" , "Predatory reptile (abbr)" .)