Get to stretch of river (5)
I believe the answer is:
reach
I believe this clue is a double definition.
'get to' is the first definition.
(synonyms)
'stretch of river' is the second definition.
(reach can mean a stretch of a river)
(Other definitions for reach that I've seen before include "compass" , "Attain - continuous extent of water" , "Attain; extend to" , "Extent of influence" , "Stretch of river: achieve" .)