Pure drunk hosting a very boisterous party (4-2)

'boisterous party' is the definition.
(rave-up can mean a large party)

'pure drunk hosting a very' is the wordplay.
'drunk' indicates anagramming the letters.
'hosting' means one lot of letters goes inside another.
'very' becomes 'v' (abbreviation).
'pure' with letters rearranged gives 'reup'.
'a'+'v'='av'
'reup' placed around 'av' is 'RAVE-UP'.