Remaining port set out (4)
I believe the answer is:
left
I believe this clue is a triple definition!
'remaining' is the first definition.
(I know that remaining can be written as left)
'port' is the second definition.
(port is the left side on a boat)
'set out' is the third definition.
(I've seen this before)
(Other definitions for left that I've seen before include "Deserted; port" , "Sailed from" , "Felt about for direction" , "The sinister side" , "Withdrew - Labour" .)