Flightless bird of South America (4)
I believe the answer is:
rhea
'flightless bird of south america' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for rhea that I've seen before include "Large flightless bird" , "Fertility goddess in ancient Greek mythology" , "Flightless bird from South America" , "Titaness" , "Fast runner" .)