One bounding area that separates two major cities (5)
I believe the answer is:
nyala
'one bounding' is the definition.
(type of antelope - antelopes jump or bound)
I don't understand the remainder of the clue.
(Other definitions for nyala that I've seen before include "African animal" , "beast" , "Large African antelope" , "crested antelope" , "South African antelope - Sudanese city" .)