Italian stream (7)
I believe the answer is:
rubicon
'italian stream' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for rubicon that I've seen before include "Caeser crossed this river in a decisive step- no going back" , "River, its crossing decisive" , "Italian stream" , "cause of conflict when crossed" , "Polish picture depicting ancient" .)