Crossword Genius

Prayer used, gain converts (5,3)

Ross

I believe the answer is:

agnus dei

'prayer' is the definition.
(Agnus Dei is an example)

'used gain converts' is the wordplay.
'converts' is an anagram indicator.
'used'+'gain'='usedgain'
'usedgain' anagrammed gives 'AGNUS DEI'.

(Other definitions for agnus dei that I've seen before include "religious piece" , "Latin liturgical prayer, Lamb of God" , "part in requiem" , "Christian emblem" , "Part of Latin Mass" .)

I've seen this clue in The Guardian.
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