Four-stringed instrument (7)
I believe the answer is:
ukulele
'four-stringed instrument' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ukulele that I've seen before include "Musical instrument once played by George Formby" , "play this?" , "George Formby's instrument" , "Small Hawaiian guitar" , "Small, four-stringed guitar" .)