Religious doctrine's final word about spiritual books (6)
I believe the answer is:
gospel
I believe this clue is a quadruple definition!!
'religious doctrine's' is the first definition.
(synonyms)
'final word' is the second definition.
The definition and answer can be both related to communication as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'about' acts as a link.
'spiritual' is the third definition.
(thesaurus)
'books' is the fourth definition.
(I've seen this before)
Can you help me to learn more?
(Other definitions for gospel that I've seen before include "Absolute truth" , "Truth (religious)" , "The teachings of Christ in a Book of the New Testament" , "Holy book" , "One of the first four Books of the New Testament" .)