British sailor returning to port (4)
I believe the answer is:
baku
'to port' is the definition.
(port in Azerbaijan)
'british sailor returning' is the wordplay.
'british' becomes 'uk' (I've seen this in other clues).
'sailor' becomes 'ab' (abbreviation for able seaman).
'returning' is a reversal indicator.
'uk'+'ab'='ukab'
'ukab' back-to-front is 'BAKU'.
(Other definitions for baku that I've seen before include "Capital of Azerbaijan on shore of Caspian Sea" , "Caspian Sea port" , "Capital city of Azerbaijan" , "Azerbaijan's capital" .)