Desperado finally banished from district backing African river (5)

I believe the answer is:

niger

'african river' is the definition.
(I've seen this before)

I can't explain the rest of the clue.

(Other definitions for niger that I've seen before include "African country dominated by the Sahara, until 1969 a French colony" , "River of West Africa" , "Major West African river" , "foreign banker" , "one flowing through Mali" .)

I've seen this clue in The Times.

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