Tree-dwelling (8)
I believe the answer is:
arboreal
'tree-dwelling' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for arboreal that I've seen before include "found in 20 [TREETOP] ?" , "Pertaining to trees" , "found in branches" , "Inhabiting trees" , "high living" .)