Religious ritual next to old capital (10)
I believe the answer is:
sacramento
'capital' is the definition.
(state capital of California)
'religious ritual next to old' is the wordplay.
'religious ritual' becomes 'sacrament' (I've seen this before).
'next to' means one lot of letters go next to another.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'sacrament'+'o'='SACRAMENTO'
(Other definitions for sacramento that I've seen before include "State capital of California" , "US city" , "port" .)