The most common and most likely answer to this crossword clue is the 8 letter word MUSICALE
I've seen this crossword clue in The Daily Telegraph
M
U
S
I
C
A
L
E
More clues leading to the result MUSICALE
Buddy explains!

The straight part
We know that "Party" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case party = musicale.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does MUSICALE mean?
MUSICALE noun- A musical entertainment, usually private and typically involving classical music