Ideas revised about animal used in holy chant (5,3)

I believe the answer is:

agnus dei

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'holy chant' is the definition.
'Agnus Dei' can be an answer for 'chant' (thesaurus). I am unsure of the 'holy' bit.

'ideas revised about animal' is the wordplay.
'revised' indicates an anagram.
'about' is an insertion indicator.
'animal' becomes 'gnu' (type of antelope).
'ideas' is an anagram of 'asdei'.
'asdei' placed around 'gnu' is 'AGNUS DEI'.

'used in' acts as a link.

Can you help me to learn more?

(Other definitions for agnus dei that I've seen before include "Section of mass" , "religious piece" , "Part of the ordinary" , "sacrificial offering" , "Christian emblem" .)

I've seen this clue in The Sun.

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