Assesses scones, quietly replacing an unspecified number (6)

I believe the answer is:

scopes

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'assesses' is the definition.
(I've seen this before)

I cannot understand how the rest of the clue works.

(Other definitions for scopes that I've seen before include "These small instruments" , "Ranges of activity" , "Optical instruments" , "Assesses" , "Sizes or ranges of subject or topics covered" .)

I've seen this clue in The Irish Times.

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