The most common and most likely answer to this crossword clue is the 11 letter word HARPSICHORD
I've seen this crossword clue in The Times
H
A
R
P
S
I
C
H
O
R
D
More clues leading to the result HARPSICHORD
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 = harpsichord.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 HARPSICHORD mean?
HARPSICHORD noun- A musical instrument with a keyboard that produces sound through a mechanical process. When the performer presses a key, a corresponding plectrum plucks a tuned string. Harpsichord originated in late medieval Europe and is one of the most important instruments used to perform Baroque music.