The most common and most likely answer to this crossword clue is the 4 letter word KOTO
K
O
T
O
Buddy explains!
The straight part
We know that "plucked instrument" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case plucked instrument = koto.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 KOTO mean?
KOTO noun- A Japanese stringed instrument having numerous strings, usually seven or thirteen, that are stretched over a convex wooden sounding board and are plucked with three plectra, worn on the thumb, index finger, and middle finger of one hand.