The most common and most likely answer to this crossword clue is the 8 letter word SINGSONG
I've seen this crossword clue in The Times
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More clues leading to the result SINGSONG
Buddy explains!

The straight part
We know that "informal musicmaking" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case informal musicmaking = singsong.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 SINGSONG mean?
SINGSONG noun- A piece of verse with a simple, song-like rhythm.
- An informal gathering at which songs are sung; a singing session.
- Bad singing or poetry.
- A drawling or monotonous tone, as of a badly executed song.
- To utter in a singsong voice.
- To write poor poetry.
- Like a piece of singsong; simple and melodic, varying in pitch (of tone of voice etc.)