Singer arranging a piece for cornet (5)
I believe the answer is:
tenor
'singer' is the definition.
(tenor is a kind of singer)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for tenor that I've seen before include "theme" , "Singer; drift" , "Placido Domingo, say" , "General course - male singer" , "Eg, Luciano Pavarotti" .)