Reed regularly broken/not broken (4)
I believe the answer is:
oboe
'reed' is the definition.
(oboe is a kind of reed)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for oboe that I've seen before include "Woodwind instrument of treble pitch" , "Player" , "Orchestral instrument" , "music producer" , "Slender double-reed instrument" .)