Get somewhere up the river (5)
I believe the answer is:
reach
'get' is the definition.
(reaching is a kind of getting)
'somewhere up the river' is the wordplay.
I cannot really see how this works, but
'up' could be 'each' (I've seen this in another clue) and 'each' is present in the answer.
'river' could be 'r' (abbreviation for river) and 'r' is present in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for reach that I've seen before include "Arrive at; extend to" , "Get to < throw up in the old" , "Grasp" , "Extend an arm" , "Get in touch" .)