African National Park's remarkably green site (9)
I believe the answer is:
serengeti
'african national park's' is the definition.
(Tanzanian national park)
'remarkably green site' is the wordplay.
'remarkably' is an anagram indicator (I've seen this in other clues).
'green'+'site'='greensite'
'greensite' with letters rearranged gives 'SERENGETI'.
(Other definitions for serengeti that I've seen before include "place to watch game" , "Tanzanian plain renowned for its wildlife" , "region in Tanzania" , "African plain noted for wildlife" , "area of Tanzania" .)