Capital once known as Salisbury (6)
I believe the answer is:
harare
'capital once known as salisbury' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for harare that I've seen before include "African capital" , "Zimbabwean capital" , "Capital of Zimbabwe" , "City in Zimbabwe" , "City once called Salisbury" .)