Cold-blooded vertebrate (7)
I believe the answer is:
reptile
'cold-blooded vertebrate' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for reptile that I've seen before include "Serpent" , "Malignant creature" , "Snake or crocodile, say" , "Eg, snake, lizard, etc" , "eg Crocodile" .)