And another thing: change liturgical book (7)
I believe the answer is:
psalter
'liturgical book' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for psalter that I've seen before include "Stapler for a book of psalms" , "Book of sacred songs" , "Book of religious songs" , "Liturgical book" , "Book used in church" .)