Violin bows (12)
I believe the answer is:
fiddlesticks
'violin bows' is the definition.
('fiddlestick' can be a synonym of 'violin bow')
This is all the clue.
(Other definitions for fiddlesticks that I've seen before include "Bother!" , "Violin bows - rubbish!" , "Rhubarb" , "tripe" , "Bows - nonsense" .)