The party to beat all parties? (6)
I believe the answer is:
thrash
This could be a double definition.
'the party' is the first definition.
(thrash can informally mean a party)
'beat all parties?' is the second definition.
'thrash' can be an answer for 'beat' (synonyms). I am unsure of the 'all parties?' bit.
'to' is the link.
Can you help me to learn more?
(Other definitions for thrash that I've seen before include "stuff" , "Decisively beat" , "tan" , "Lay on - party" , "Wallop" .)