The most common and most likely answer to this crossword clue is the 9 letter word HARMONICA
I've seen this crossword clue in Financial Times
H
A
R
M
O
N
I
C
A
More clues leading to the result HARMONICA
- New chairman retaining old producer of notes
- Not half hard-up, money's in cash one's blown
- Music maker’s nickname called out, with cheer echoing
- A lot of damage on front of girl’s instrument
- After theatre, even in coma playing instrument
- Organ damage on vicar’s insides
- Instrument damage? Toss a coin!
- Saintly female on instrument, not piano — much smaller one
- Play this on 1 March badly, then 1 April
- Instrument playing in a march I found discordant
Buddy explains!

The straight part
We know that "instrument" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case instrument = harmonica.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 HARMONICA mean?
HARMONICA noun- A musical wind instrument with a series of holes for the player to blow into, each hole producing a different note
- A musical instrument, consisting of a series of hemispherical glasses which, by touching the edges with the dampened finger, give forth the tones.
- A toy instrument of strips of glass or metal hung on two tapes, and struck with hammers.