Riotous party in joint with drink (5-2)
I believe the answer is:
knees-up
'riotous party' is the definition.
(I've seen this before)
'joint with drink' is the wordplay.
'joint' becomes 'knee' (knee is a kind of joint**).
'with' says to put letters next to each other.
'drink' becomes 'sup' (I've seen this before).
'knee'+'sup'='KNEES-UP'
'in' is the link.
(Other definitions for knees-up that I've seen before include "Lively party (colloq.)" , "Informal party with dancing" , "Dance with Mother Brown" , "Lively informal party" , "Riotous dance - party" .)