Body of knowledge lost on religious experiences, primarily (4)
I believe the answer is:
lore
'body of knowledge' is the definition.
(I've seen this in another clue)
'lost on religious experiences primarily' is the wordplay.
'primarily' indicates taking the first letters.
The initial letters of 'lost on religious experiences' is 'LORE'.
(Other definitions for lore that I've seen before include "Traditional knowledge" , "Role for learning" , "Body of knowledge" , "Old learning" , "Ancient learning" .)