The most common and most likely answer to this crossword clue is the 5 letter word REBEC
I've seen this crossword clue in The Guardian
R
E
B
E
C
More clues leading to the result REBEC
- Something played live in playing field
- One of the viols – who’d mutiny with base doubled?
- Old music-maker‘s
- Something to restore, because it’s an old instrument
- Old instrument has gone into fire – be careful!
- Old instrument providing backing for popular reggae and superb dance music
- Damage half of cerebellum with old instrument
- Old music-maker is dissident Liberal turning Conservative
- In miniature, because an instrument
Buddy explains!

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 REBEC mean?
REBEC noun- An early three-stringed instrument, somewhat like a simple violin only pear shaped, played with a bow and used in Medieval and the early Renaissance eras.