Forecast the left with finality (7)
I believe the answer is:
portend
'forecast' is the definition.
(I know that forecast can be written as portend)
'left with finality' is the wordplay.
'left' becomes 'port' (left side of a ship - opposite of starboard).
'with' is a charade indicator (letters next to each other).
'finality' becomes 'end' (I can't explain this - if you can you should give a lot more credence to this answer).
'port'+'end'='PORTEND'
'the' acts as a link.
Can you help me to learn more?
(Other definitions for portend that I've seen before include "forecast" , "Give warning" , "Be a sign of something to come" , "Omen" , "Signal" .)