Lizard type (6)
(Other definitions for iguana that I've seen before include "Tropical tree-lizard" , "Large tree-climbing specimen of 5 down in tropical America" , "Arboreal lizard of S America" , "Type of lizard" , "Lizard Darwin found in the Galapagos" .)
'lizard type' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for gecko that I've seen before include "Wall Street character" , "Lizard than can't blink" , "Small lizard with adhesive foot-pads" , "Lizard with adhesive toes" , "Cold-blooded type" .)
(Other definitions for monitor that I've seen before include "Person or device for observing and checking" , "Keep a watching brief" , "Keep under surveillance" , "Police" , "Vet" .)
(Other definitions for chameleon that I've seen before include "person who's changeable" , "Lizard that can change its colours" , "fickle person" , "Lizard able to change its skin colour" , "Someone who changes position to suit the situation" .)