Pitch perfect opera singer by all conclusions (3)
I believe the answer is:
tar
'pitch' is the definition.
(I know that pitch can be written as tar)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for tar that I've seen before include "Road-dressing for a sailor?" , "Crewman" , "Viscous mixture - sailor" , "Black substance, used on roads" , "Smoker's black deposit" .)