The most common and most likely answer to this crossword clue is the 5 letter word RAVES
I've seen this crossword clue in The Guardian
R
A
V
E
S
More clues leading to the result RAVES
Buddy explains!

The straight part
We know that "Parties" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case parties = raves.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 RAVES mean?
RAVES noun- An enthusiastic review (such as of a play).
- An all-night dance party with electronic dance music (techno, trance, drum and bass etc.) and possibly drug use.
- The genres of electronic dance music usually associated with rave parties.
- To wander in mind or intellect; to be delirious; to talk or act irrationally; to be wild, furious, or raging.
- To speak or write wildly or incoherently.
- To talk with unreasonable enthusiasm or excessive passion or excitement; followed by about, of, or (formerly) on.
- To rush wildly or furiously.
- To attend a rave (dance party).
- One of the upper side pieces of the frame of a wagon body or a sleigh.