Sound mark of childish progress (6)

I believe the answer is:

report

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'sound' is the definition.
(report is a kind of sound)

I cannot understand how the rest of the clue works.

(Other definitions for report that I've seen before include "Complain about; noise" , "Make a complaint about (someone)" , "Declaration" , "Sharp noise; rumour" , "Announce; rumour" .)

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

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