SA port, but no capital city (5)
I believe the answer is:
'city' is the definition.
(urban means relating to a city)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(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" .)