Settle a row on a river (7)
I believe the answer is:
arrange
'settle' is the definition.
(I know that settle is a more specific form of the action arrange)
'a row on a river' is the wordplay.
'a row' becomes 'range' (range can mean a row or chain of things).
'on' says to put letters next to each other.
'river' becomes 'r' (abbreviation for river).
'a'+'r'='ar'
'range' after 'ar' is 'ARRANGE'.
(Other definitions for arrange that I've seen before include "Orchestrate - order" , "Sort" , "Bring about or put in order" , "Marshal" , "Order, plan or design" .)