One who should know the score (9)

I believe the answer is:

conductor

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'one who should know the score' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.

This is the entire clue.

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(Other definitions for conductor that I've seen before include "Train guard" , "One should receive the current" , "Musician" , "who may wave his hands about?" , "See 6" .)

I've seen this clue in The Globe and Mail.

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