Lost Biro in a capital city in East Africa (7)

I believe the answer is:

nairobi

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'city in east africa' is the definition.
(capital of Kenya)

'lost biro in a' is the wordplay.
'lost' is an anagram indicator.
'biro'+'in'+'a'='biroina'
'biroina' anagrammed gives 'NAIROBI'.

'capital' is the link.
This may not be correct. It may be part of another bit of the clue.

Can you help me to learn more?

(Other definitions for nairobi that I've seen before include "The capital of Kenya (7)" , "Flat round object" , "Kenyan city" , "City of Kenya" , "Kenyan capital" .)

I've seen this clue in the Sydney Morning Herald.

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