Composition book held by setter’s torn at the corner (5)

I believe the answer is:

motet

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

I cannot understand how the remainder of the clue works.

(Other definitions for motet that I've seen before include "Anthem or church cantata" , "Certain one is morally superior" , "10 [COMPOSITION]" , "Unaccompanied choral composition with sacred lyrics" , "Short piece of church choral music" .)

I've seen this clue in The Hindu.

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