Instrument with a double reed (4)
I believe the answer is:
oboe
'instrument with a double reed' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for oboe that I've seen before include "Double-reeded woodwind instrument" , "Double-reed woodwind" , "bit of wind" , "Woodwind instrument of treble pitch" , "Instrument used in 1d" .)