Spanish nobleman and mum's mum on Scottish river (7)
I believe the answer is:
grandee
'spanish nobleman' is the definition.
(I've seen this before)
'mum's mum on scottish river' is the wordplay.
'mum's mum' becomes 'gran' (I've seen this before).
'on' says to put letters next to each other.
'scottish river' becomes 'dee' (I've seen this before).
'gran'+'dee'='GRANDEE'
'and' is the link.
(Other definitions for grandee that I've seen before include "Person of high rank" , "A Spanish or Portuguese noble" , "Person of eminence" , "aristocrat" , "Enraged (anag) - Spanish nobleman" .)