Church has a book to sing (5)
I believe the answer is:
chant
'sing' is the definition.
(chanting is a kind of singing)
'church has a book' is the wordplay.
'church' becomes 'ch' (common abbreviation).
'has' is a charade indicator (letters next to each other).
'book' becomes 'nt' (I've seen this in other clues**).
'ch'+'a'+'nt'='CHANT'
'to' acts as a link.
(Other definitions for chant that I've seen before include "Incantatory song" , "Gregorian song?" , "Recite singingly" , "Mantra" , "Intone - recite" .)