Religious work that is found in school group (5)
I believe the answer is:
pieta
'religious work' is the definition.
(image of the Virgin Mary holding Jesus' body)
'that is found in school group' is the wordplay.
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'found in' indicates putting letters inside.
'school group' becomes 'pta' (I've seen this in another clue).
'ie' put inside 'pta' is 'PIETA'.
(Other definitions for pieta that I've seen before include "Statue of Mary with the dead Christ" , "Statue of Virgin Mary" , "Image of Mary with the body of Christ" , "Religious representation" , "mournful image" .)