Take things to extremes when finished with the party (6)
I believe the answer is:
overdo
'take things to extremes' is the definition.
I can't tell whether this definition defines the answer.
'finished with the party' is the wordplay.
'finished' becomes 'over' (over can mean finished or ended).
'with' means one lot of letters go next to another.
'the party' becomes 'do' (do can informally mean a party).
'over'+'do'='OVERDO'
'when' acts as a link.
Can you help me to learn more?
(Other definitions for overdo that I've seen before include "Be excessive, perhaps cook too much" , "Carry too far" , "Be excessive, say cook too long" , "Maybe burn" , "Take too far" .)