Novel idea to limit suffering sung in prayer (5,3)
I believe the answer is:
agnus dei
'prayer' is the definition.
(Agnus Dei is an example)
'novel idea to limit suffering sung' is the wordplay.
'novel' indicates anagramming the letters (letters in a new or novel order).
'to limit' means one lot of letters goes inside another (outside letters limit or restrain others).
'suffering' indicates anagramming the letters.
'idea' anagrammed gives 'adei'.
'sung' is an anagram of 'gnus'.
'adei' enclosing 'gnus' is 'AGNUS DEI'.
'in' acts as a link.
(Other definitions for agnus dei that I've seen before include "part in requiem" , "sacrificial offering" , "Section of mass" , "religious piece" , "Part of Latin Mass" .)