Green site turning plain (9)
I believe the answer is:
serengeti
'plain' is the definition.
(I know that Serengeti is a plain)
'green site turning' is the wordplay.
'turning' is an anagram indicator.
'green'+'site'='greensite'
'greensite' with letters rearranged gives 'SERENGETI'.
(Other definitions for serengeti that I've seen before include "place to watch game" , "Tanzanian wildlife area" , "African ecosystem" , "area of Tanzania" , "Wildlife-rich region of Africa" .)