Arboreal Aussie (5)
I believe the answer is:
koala
'arboreal aussie' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for koala that I've seen before include "Australian marsupial which lives on eucalyptus leaves" , "Tree-hugger" , "Australian animal" , "Arboreal Australian native" , "Arboreal marsupial" .)