Religious work that involves one more duty (11)

I believe the answer is:

deuteronomy

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'religious work' is the definition.
The definition suggests a singular noun which matches the answer.

'involves one more duty' is the wordplay.
'involves' indicates an anagram.
'one'+'more'+'duty'='onemoreduty'
'onemoreduty' is an anagram of 'DEUTERONOMY'.

'that' is the link.

Can you help me to learn more?

(Other definitions for deuteronomy that I've seen before include "Old cat in T.S.Eliot's" , "OT book" , "Fifth book of the Bible" , "Book of the Old Testament" .)

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

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