Die by water, having fallen crossing river (5)
I believe the answer is:
drown
'die' is the definition.
(I know that drown is a more specific form of die)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for drown that I've seen before include "Flood (an area)" , "Completely conceal" , "Die in water" , "Perish in water" , "Die from submersion in liquid" .)