Small guitar (7)
I believe the answer is:
ukulele
'small guitar' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for ukulele that I've seen before include "George Formby's little guitar" , "Small type of guitar" , "Instrument from Hawaii" , "Small guiter - George Formby played it" , "Small guitar as played by George Formby" .)