Nut enters rising river — that's devotion for you (6)
I believe the answer is:
novena
'that's devotion for you' is the definition.
(type of Christian devotional praying)
'nut enters rising river' is the wordplay.
'nut' becomes 'en' ('nut' is printers' slang for an en space).
'enters' is an insertion indicator.
'rising' shows that the letters should be reversed in order (going up in a down clue).
'river' becomes 'avon' (I've seen this before).
'avon' reversed gives 'nova'.
'en' inserted within 'nova' is 'NOVENA'.
(Other definitions for novena that I've seen before include "Nine-day religious devotion" , "RC prayers over 9 days" , "Nine consecutive days of prayer or worship" , "Sequence of prayers" , "Nine-day ritual" .)