The most common and most likely answer to this crossword clue is the 5 letter word BUGLE
I've seen this crossword clue in Financial Times
B
U
G
L
E
More clues leading to the result BUGLE
- Listen to the French horn
- Plant leaf half destroyed by insect
- Mistake throwing out new instrument
- Blue and golden odd bits
- Cause irritation with the French horn
- Not right to enter a property to steal a musical instrument
- Vacuous life beyond disease, blow it!
- Make a dreadful mistake losing new horn
- Bit of brass to annoy the French
- Missing a note, make a mess of horn
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 = bugle.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 BUGLE mean?
BUGLE noun- A horn used by hunters.
- A simple brass instrument consisting of a horn with no valves, playing only pitches in its harmonic series
- A plant in the family Lamiaceae grown as a ground cover, Ajuga reptans, and other plants in the genus Ajuga.
- Anything shaped like a bugle, round or conical and having a bell on one end.
- To announce, sing, or cry in the manner of a musical bugle
- A tubular glass or plastic bead sewn onto clothes as a decorative trim
- Jet-black
- A sort of wild ox; a buffalo.