Party with great chat (6)
I believe the answer is:
confab
'chat' is the definition.
('confab' can be a synonym of 'chat')
'party with great' is the wordplay.
'party' becomes 'con' (abbreviation for Conservatives).
'with' means one lot of letters go next to another.
'great' becomes 'fab' (I've seen this in other clues).
'con'+'fab'='CONFAB'
(Other definitions for confab that I've seen before include "jaw" , "Informal discussion (colloq.)" , "Exchange" , "Chat (informal)" , "casual conversation" .)