Bones intended, it's said, for special religious ceremonies (10)

'religious ceremonies' is the definition.
(sacrament is a kind of religious ceremony)

'bones intended it's said for special' is the wordplay.
'bones' becomes 'sacra' (sacrum is a kind of bone**).
'intended' becomes 'meant' (meaning is a kind of intending).
'it's said' shows a homophone (sound like).
'for' is a charade indicator (letters next to each other).
'special' becomes 's' (common abbreviation as in Special Air Service).
'meant' is a homophone of 'ment'.
'sacra'+'ment'+'s'='SACRAMENTS'