Ho hum, pedestrian score checker (5-6)

I believe the answer is:

sight-reader

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'score checker' is the definition.
The definition suggests a singular noun which matches the answer.

'ho hum pedestrian' is the wordplay.
'ho hum' becomes 'sigh' (I can't explain this - if you can you should give a lot more credence to this answer).
'pedestrian' becomes 'treader' (I've seen this in another clue).
'sigh'+'treader'='SIGHT-READER'

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(Other definitions for sight-reader that I've seen before include "one performing without preparation" , "Very able musician" .)

I've seen this clue in The Times.

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