The most common and most likely answer to this crossword clue is the 12 letter word HOOTENANNIES
I've seen this crossword clue in The Daily Telegraph
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More clues leading to the result HOOTENANNIES
Buddy explains!

The straight part
We know that "parties with singing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case parties with singing = hootenannies.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 HOOTENANNIES mean?
HOOTENANNIES noun- An informal, festive performance by folk singers, often including audience participation with the use of acoustic instruments.
- A placeholder word for a nonspecific or forgotten thing (see thingamajig, whatchamacallit)