Port from which a U.K. sailor returns (4)
I believe the answer is:
baku
'port' is the definition.
(port in Azerbaijan)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for baku that I've seen before include "Caspian Sea port" , "Capital of Azerbaijan on shore of Caspian Sea" , "Azerbaijan's capital" , "Capital city of Azerbaijan" .)