Come clean about one written about female saints (7)
I believe the answer is:
confess
'come clean' is the definition.
(thesaurus)
'about one written about female saints' is the wordplay.
'about' becomes 'c' (abbreviation for 'circa'**).
'written about' means one lot of letters goes inside another.
'female' becomes 'f' (abbreviation).
'saints' becomes 'ss'.
'one' placed around 'f' is 'onfe'.
'c'+'onfe'+'ss'='CONFESS'
(Other definitions for confess that I've seen before include "Admit (to crime)" , "Admit (to wrongdoing)" , "Concede" , "Tell a priest one's sins" , "Plead guilty (in order to receive absolution?)" .)