One excused master class (5)

I believe the answer is:

genus

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'class' is the definition.
(I've seen this in another clue)

I can't explain the rest of the clue.

(Other definitions for genus that I've seen before include "Kind or sort of" , "Taxonomic class between family and species" , "species grouped together" , "group of organisms" , "The Homo of Homo sapiens?" .)

I've seen this clue in The Sun.

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