Get to stretch of water (5)
I believe the answer is:
reach
I believe this clue is a triple definition!
'get to' is the first definition.
('reach' can be a synonym of 'get to')
'stretch' is the second definition.
('reach' can be a synonym of 'stretch')
'of' acts as a link.
'water' is the third definition.
(I have seen 'open water' mean 'reach' so perhaps 'water' could also mean 'reach')
(Other definitions for reach that I've seen before include "Succeed in getting to" , "Get as far as" , "Stretch of river: achieve" , "Attain - make contact with" , "Get in touch" .)