It's left for the sailor (4)
I believe the answer is:
port
This might be a double definition.
'it's left' is the first definition.
(left side of a ship - opposite of starboard)
'sailor' is the second definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'for the' acts as a link.
Can you help me to learn more?
(Other definitions for port that I've seen before include "Drink passed to the left" , "Rio, perhaps" , "Dessert wine" , "Stanley perhaps" , "Bordeaux, say" .)