Violin tuner (3)
I believe the answer is:
peg
'violin tuner' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for peg that I've seen before include "The girl to hold a hat" , "Brandy and soda drink measure" , "Short pin or bolt" , "This leg is artificial" , "Wooden or plastic pin for hanging clothes" .)