Working sailor came about to enter port (4)
I believe the answer is:
oban
'port' is the definition.
(Oban is a Scottish port)
'working sailor came about to enter' is the wordplay.
'working' becomes 'on' (e.g. a machine is working or on).
'sailor' becomes 'ab' (abbreviation for able seaman).
'came about' says the letters should be written in reverse (I've seen 'coming about' mean this (about can mean backwards or around)).
'to enter' indicates putting letters inside.
'ab' written backwards gives 'ba'.
'on' placed around 'ba' is 'OBAN'.
(Other definitions for oban that I've seen before include "Argyll town" , "Western Scottish port" , "Port and holiday centre on the west coast of Scotland" , "Argyll and Bute resort" , "Northern port" .)