A Grecian throng reworked religious song (9,5)

I believe the answer is:

gregorian chant

'religious song' is the definition.
(Gregorian chant is an example)

'a grecian throng reworked' is the wordplay.
'reworked' indicates an anagram.
'a'+'grecian'+'throng'='agrecianthrong'
'agrecianthrong' with letters rearranged gives 'GREGORIAN CHANT'.

(Other definitions for gregorian chant that I've seen before include "variety of plainsong" , "Medieval plainsong" .)

I've seen this clue in The Telegraph.

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