Quickly read exam. It's most inadequate! (8)

I believe the answer is:

scantest

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'most inadequate' is the definition.
Both the definition and answer are superlative adjectives. Maybe you can see an association between them that I don't see?

'quickly read exam' is the wordplay.
'quickly read' becomes 'scan' (to scan something is to read it quickly).
'exam' becomes 'test' (synonyms).
'scan'+'test'='SCANTEST'

'it's' is the link.

Can you help me to learn more?

(Another definition for scantest that I've seen is " Most deficient".)

I've seen this clue in the Sydney Morning Herald.

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