Arboreal lizard (6)
I believe the answer is:
iguana
'arboreal lizard' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for iguana that I've seen before include "Arboreal lizard of S America" , "Lizard Darwin found in the Galapagos" , "Large lizard of tropical Amercia" , "Large tree-climbing specimen of 5 down in tropical America" , "Animal" .)