Get to part of the river (5)
I believe the answer is:
reach
This might be a double definition.
'get to' is the first definition.
(synonyms)
'part of the river' is the second definition.
'reach' can be an answer for 'part' (reach is a kind of part). I am unsure of the 'of the river' bit.
Can you help me to learn more?
(Other definitions for reach that I've seen before include "Hands up" , "Hit" , "stretch of canal between locks" , "Stretch of river: achieve" , "Scope; get to" .)