SA port, but no capital city (5)

I believe the answer is:

urban

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'city' is the definition.
(urban means relating to a city)

I cannot understand how the remainder of the clue works.

(Other definitions for urban that I've seen before include "One of eight popes" , "Relating to towns" , "Relating to city life" , "Town (adj.)" , "Name adopted by eight popes: built-up" .)

I've seen this clue in The Sunday Times and The Times.

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