Composition book held by setter’s torn at the corner (5)
I believe the answer is:
motet
'composition' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(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" .)