Left the harbour? (4)
I believe the answer is:
port
I believe this is a double definition.
'left' is the first definition.
(left side of a ship - opposite of starboard)
'the harbour?' is the second definition.
(harbour is a kind of port)
(Other definitions for port that I've seen before include "Left, opening, wine" , "Saint John, for one, > left" , "Sweet dark red fortified wine taken after meal" , "Light enough to carry" , "Wine left at sea ?" .)