Plain ties and green buckle (9)
I believe the answer is:
serengeti
'plain' is the definition.
(I know that Serengeti is a plain)
'ties and green buckle' is the wordplay.
'and' means one lot of letters go next to another.
'buckle' indicates an anagram.
'ties' put after 'green' is 'greenties'.
'greenties' is an anagram of 'SERENGETI'.
(Other definitions for serengeti that I've seen before include "Tanzanian wildlife area" , "Wildlife preserve (and National Park) in Tanzania" , "Tanzanian national park area" , "African plain noted for wildlife" , "area of Tanzania" .)