By a river, spread out with a liturgical book (8)
I believe the answer is:
breviary
'liturgical book' is the definition.
'breviary' can be an answer for 'book' (breviary is a kind of book). I am not certain of the 'liturgical' bit.
'by a river spread out with a' is the wordplay.
'spread out with' is an anagram indicator (I've seen 'spreading out' mean this).
'by'+'river'='byriver'
'byriver' anagrammed with 'a' can make 'BREVIARY'.
Can you help me to learn more?
(Other definitions for breviary that I've seen before include "Book of daily prayer for RC priests" , "Priest's book of prayers found in river bay" , "Catholic priest's book of daily prayers" , "service manual" , "Church book" .)