Country sailor returns to port (4)
I believe the answer is:
baku
'to port' is the definition.
(port in Azerbaijan)
'country sailor returns' is the wordplay.
'country' becomes 'UK' (United Kingdom).
'sailor' becomes 'ab' (abbreviation for able seaman).
'returns' says the letters should be written in reverse.
'uk'+'ab'='ukab'
'ukab' backwards is 'BAKU'.
(Other definitions for baku that I've seen before include "Azerbaijan's capital" , "Capital city of Azerbaijan" , "Capital of Azerbaijan on shore of Caspian Sea" , "Caspian Sea port" .)