Respectful term is upriver? (3)
I believe the answer is:
sir
This clue could be a double definition.
'respectful term' is the first definition.
(I've seen this in another clue)
'upriver?' is the second definition.
Both the answer and definition are singular nouns.
Perhaps there's a link between them I don't understand?
'is' is the link.
Can you help me to learn more?
(Other definitions for sir that I've seen before include "Knight's prefix" , "Gentleman's form of address" , "Knight's title" , "Honorary male title" , "Form of address for a knight" .)