Very famous section of Rubicon I crossed (6)
I believe the answer is:
iconic
'very famous' is the definition.
(I've seen this before)
'section of rubicon i crossed' is the wordplay.
'section of' indicates a hidden word.
'ICONIC' is hidden within 'rubicon i crossed'.
(Other definitions for iconic that I've seen before include "(Of paintings/statues) in a fixed conventional style" , "Serving as a significant symbol" , "Emblematic, representative" , "Having the nature of a sacred image" , "conventional type" .)