In an operatic voice, except for single bum note (8)
I believe the answer is:
baritone
'in an operatic voice' is the definition.
I can't tell whether this definition defines the answer.
'except for single bum note' is the wordplay.
'except for' becomes 'bar' (I've seen this in another clue).
'single' becomes 'I' (I as in one).
'bum' is an anagram indicator (bum can mean faulty or wrong).
'note' anagrammed gives 'tone'.
'bar'+'i'+'tone'='BARITONE'
Can you help me to learn more?
(Other definitions for baritone that I've seen before include "One who can sing" , "Second lowest male singing voice" , "Male voice between bass and tenor" , "Male singer between tenor and bass" , "Adult male singing voice" .)