Crested reptile (6)
I believe the answer is:
iguana
'crested reptile' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for iguana that I've seen before include "Something like a monitor" , "The Night of the ---, (T. Williams)" , "Could be a monitor" , "Large tree-climbing specimen of 5 down in tropical America" , "cold-blooded customer!" .)