Crested reptile (6)
I believe the answer is:
iguana
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">crested reptile</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(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!" .)