Cult's keeping empty religiose confidences (7)
I believe the answer is:
secrets
'confidences' is the definition.
(I've seen this in another clue)
'cult's keeping empty religiose' is the wordplay.
'cult's' becomes 'sect's' (religious sect).
'keeping' means one lot of letters goes inside another.
'empty' says to hollow out the word (remove centre letters).
'religiose' with its middle removed is 're'.
'sects' placed around 're' is 'SECRETS'.
(Other definitions for secrets that I've seen before include "Hidden facts" , "Undivulged facts" , "Confidential matters" , "Concealed facts" , "Confidential data" .)