Sailor also called port in Japan (5)
I believe the answer is:
osaka
'port in japan' is the definition.
(I've seen this in another clue)
'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 "Japanese port, Bay" , "Japanese city near Kobe" , "Japanese port city" , "Place" , "in east Asia" .)