Tiger seen roaming where lion holds sway (9)
I believe the answer is:
serengeti
'where lion holds sway' is the definition.
(some lions live in the Serengeti)
'tiger seen roaming' is the wordplay.
'roaming' is an anagram indicator.
'tiger'+'seen'='tigerseen'
'tigerseen' with letters rearranged gives 'SERENGETI'.
(Other definitions for serengeti that I've seen before include "reserve for game" , "Tiger seen in Tanzania's great National Park" , "region in Tanzania" , "Afr. plain; green site (anag.)" , "Wildlife preserve (and National Park) in Tanzania" .)