Stretch up the river? (5)
I believe the answer is:
reach
This could be a double definition.
'stretch up' is the first definition.
'reach' can be an answer for 'stretch' (I've seen this in another clue). I am not sure about the 'up' bit.
'river?' is the second definition.
(I know that reach is a type of river)
'the' acts as a link.
Can you help me to learn more?
(Other definitions for reach that I've seen before include "Come up to - stretch between bends" , "Arrive at a point" , "stretch of canal between locks" , "Get to < throw up in the old" , "range" .)