He ruins the drink and the game (10)
I believe the answer is:
spoilsport
'he ruins' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'drink and the game' is the wordplay.
'drink' becomes 'port' (port is a kind of drink).
'and' means one lot of letters go next to another.
'the game' becomes 'spoils' (I am not sure about this - if you are sure you should believe this answer much more).
'port' after 'spoils' is 'SPOILSPORT'.
'the' is the link.
Can you help me to learn more?
(Other definitions for spoilsport that I've seen before include "nark" , "Killjoy" , "misery" , "Wet blanket" , "Party pooper" .)