Flightless bird of the pampas (4)
I believe the answer is:
rhea
'flightless bird of the pampas' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for rhea that I've seen before include "Large S. American bird" , "Small 'ostrich'" , "Large flightless bird" , "S. Amer. flightless bird" , "China grass" .)