Fateful crossing point (7)
I believe the answer is:
rubicon
'fateful crossing point' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for rubicon that I've seen before include "Caesar crossed this river in an irreversible step" , "Caesar's point of no return" , "River symbolically crossed" , "River, its crossing decisive" , "Polish picture depicting ancient" .)