Grassy plains (6)
I believe the answer is:
pampas
'grassy plains' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for pampas that I've seen before include "Vast plains of South America" , "South American plain" , "7" , "Treeless plain(s)" , "Prairies (with grass)" .)