Bwana? Unsettling nomenclature for an individual of rank (5)

I believe the answer is:

nawab

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'nomenclature for an individual of rank' is the definition.
I can't judge whether this defines the answer.

'bwana? unsettling' is the wordplay.
'unsettling' is an anagram indicator.
'bwana' with letters rearranged gives 'NAWAB'.

Can you help me to learn more?

(Other definitions for nawab that I've seen before include "Muslim prince in India" , "Indian ruler" , "Distinguished Muslim" , "Native governor in India; bwana (anag.)" , "Old governor" .)

I've seen this clue in The Independent.

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