Noble fellow with female relation by river (7)
I believe the answer is:
grandee
'noble fellow' is the definition.
(grandee can mean a noble person)
'female relation by river' is the wordplay.
'female relation' becomes 'gran' (short for grandmother).
'by' means one lot of letters go next to another.
'river' becomes 'dee' (River Dee).
'gran'+'dee'='GRANDEE'
'with' is the link.
(Other definitions for grandee that I've seen before include "VIP" , "Eminent man" , "European lord" , "Enraged (anag) - Spanish nobleman" , "man of high rank abroad" .)