Revised text about religious feast, as released (9)
I believe the answer is:
recension
'revised text about religious feast as released' is the definition.
I can't judge whether this defines the answer.
'text about religious feast as released' is the wordplay.
'text about' becomes 're' (I am not sure about this - if you are sure you should believe this answer much more).
'religious feast' becomes 'ascension' (I've seen this before).
'released' indicates named letters should be taken away.
'ascension' with 'as' taken out is 'cension'.
're'+'cension'='RECENSION'
Can you help me to learn more?
(Another definition for recension that I've seen is " Revision (of a text)".)