River, point of no return (7)
I believe the answer is:
I believe this is a double definition.
'river' is the first definition.
(I've seen this before)
'point of no return' is the second definition.
(as in the phrase 'crossing the Rubicon')
(Other definitions for rubicon that I've seen before include "Caesar crossed this river to take irrevocable step" , "River symbolically crossed" , "Caeser crossed this river in a decisive step- no going back" , "Caesar's point of no return" , "Caesar got over this" .)