Left on ship aim to make forecast (7)
I believe the answer is:
portend
'forecast' is the definition.
(I know that forecast can be written as portend)
'left on ship aim' is the wordplay.
I cannot quite understand how this works, but
'left' could be 'port' (left side of a ship - opposite of starboard) and 'port' is present in the answer.
'aim' could be 'end' (both can mean a goal or purpose) and 'end' is found in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'to make' acts as a link.
Can you help me to learn more?
(Other definitions for portend that I've seen before include "Foreshadow" , "forecast" , "Herald" , "Signal" , "Threaten" .)