Avian Aussie (3)
I believe the answer is:
emu
'avian aussie' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for emu that I've seen before include "Australian non-flyer" , "Fast runner in Oz" , "Australian running bird." , "Aussie bird" , "that doesn't get off the ground" .)