Booty left on boat by party pooper (10)
I believe the answer is:
spoilsport
'party pooper' is the definition.
(synonyms)
'booty left on' is the wordplay.
'booty' becomes 'spoils' (both can mean the proceeds or prize from something).
'left' becomes 'port' (left side of a ship - opposite of starboard).
'on' is a charade indicator (letters next to each other).
'spoils'+'port'='SPOILSPORT'
'boat by' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for spoilsport that I've seen before include "One marring others' pleasure" , "One who ruins others' enjoyment" , "misery" , "One who reduces others' pleasure" , "One who won't play?" .)