Freak to propose entering river (7)
I believe the answer is:
devotee
'freak' is the definition.
(thesaurus)
'propose entering river' is the wordplay.
'propose' becomes 'vote' (**).
'entering' means one lot of letters goes inside another.
'river' becomes 'dee' (River Dee).
'vote' placed into 'dee' is 'DEVOTEE'.
'to' is the link.
(Other definitions for devotee that I've seen before include "Zealous follower" , "Keen admirer" , "Ardent follower and admirer" , "An enthusiastic admirer and supporter" , "Person who is utterly loyal and committed to someone" .)