Flightless Australian bird (3)
I believe the answer is:
emu
'flightless australian bird' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for emu that I've seen before include "it can't get off the ground" , "unit of measurement" , "Ostrich-like bird" , "Large Australian flightless bird" , "Long-necked bird" .)