Busoni piece usually without conductor (3)
I believe the answer is:
bus
'conductor' is the definition.
(bus is a kind of conductor)
'busoni piece usually without' is the wordplay.
I cannot really understand how this works, but
'piece' could be 'b' (abbreviation for bishop) and 'b' is found in the answer.
The remaining letters 'us' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for bus that I've seen before include "eg Double-decker" , "Mode of public transport" , "Public transport vehicle" , "Of projectiles; (go) mad (slang)" , "Something caught" .)