Eucalyptus dweller (5)
I believe the answer is:
koala
'eucalyptus dweller' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for koala that I've seen before include "Aussie tree-climber" , "Marsupial climber" , "small bear" , "Bear-like Australian marsupial" , "Arboreal Australian native" .)