Say, religious text without liturgical headings is really bad! (9)
I believe the answer is:
egregious
'really bad' is the definition.
Both the definition and answer are adjectives. Maybe there's a link between them I don't understand?
'say religious text without liturgical headings' is the wordplay.
I cannot really see how this works, but
'say' could be 'eg' (both can mean 'for example') and 'eg' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
'is' is the link.
Can you help me to learn more?
(Other definitions for egregious that I've seen before include "Outstandingly bad" , "Outstandingly villainous" , "Notorious" , "Insufferable" , "Outstanding, outrageous" .)