Sailor also called foreign port (5)
I believe the answer is:
osaka
'foreign port' is the definition.
(port in Japan)
'sailor also called' is the wordplay.
'sailor' becomes 'os' (ordinary seaman).
'also called' becomes 'aka' (also known as).
'os'+'aka'='OSAKA'
(Other definitions for osaka that I've seen before include "Third most populous Japanese city" , "Kinki's capital" , "Place" , "Japanese metropolis" , "Large city and port in Japan" .)