River begins rising here in northern Europe (5)
I believe the answer is:
rhine
'river' is the definition.
(I know that Rhine is a river)
'begins rising here in northern europe' is the wordplay.
'begins' says to take the initial letters.
'europe' becomes 'E' (abbreviation eg in E number).
The first letters of 'rising here in northern' is 'rhin'.
'rhin'+'e'='RHINE'
(Other definitions for rhine that I've seen before include "River rising in Alps, with mouth at Rotterdam" , "Great river in Germany with Lorelei Rock" , "fed by 8 [RHUR]" , "Major European river" , "Ring river (Wagner)" .)