Instrument with a conical bore (4)
I believe the answer is:
oboe
'instrument with a conical bore' 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 "Musical instrument" , "Double-reeded woodwind instrument" , "Double-reed woodwind" , "Source of music" , "Player" .)