Arrive at part of the river (5)
I believe the answer is:
reach
This could be a double definition.
'arrive at part' is the first definition.
'reach' can be an answer for 'arrive' (reaching is a kind of arriving). I am unsure of the 'at part' bit.
'river' is the second definition.
(I know that reach is a type of river)
'of the' is the link.
Can you help me to learn more?
(Other definitions for reach that I've seen before include "Come to - stretch of river" , "Hit" , "Arrive at - stretch of river" , "Hands up" , "Get in touch" .)