American arboreal lizards (7)
I believe the answer is:
iguanas
'american arboreal lizards' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for iguanas that I've seen before include "Monitors" , "American arboreal lizards" , "Tropical tree lizards" , "Asia gun (anag.)" , "beasts" .)