The most common and most likely answer to this crossword clue is the 11 letter word CONCERTINAS
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Buddy explains!
The straight part
We know that "More than one instrument" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case more than one instrument = concertinas.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 CONCERTINAS mean?
CONCERTINAS noun- A musical instrument, like the various accordions, that is a member of the free-reed family of musical instruments, typically having buttons on both ends.
- Something resembling a concertina, such as a folded book, a bus door or a set of picture frames that are folded together.
- Coiled barbed wire for use as an obstacle.
- A type of booklet label, consisting of up to 32 pages of booklet as an insert.
- To become compressed into a shape reminiscent of a concertina
- To be drawn closer and farther apart repeatedly, or up and down, as if situated on a working concertina's folds