Reach a river, somehow (6)
I believe the answer is:
arrive
'reach' is the definition.
(I know that reach is a more specific form of arrive)
'a river somehow' is the wordplay.
'somehow' is an anagram indicator.
'river' is an anagram of 'rrive'.
'a'+'rrive'='ARRIVE'
(Other definitions for arrive that I've seen before include "Reach destination or succeed" , "Come to a destination" , "Turn up" , "Reach a place" , "(Of time) come about" .)