The most common and most likely answer to this crossword clue is the 7 letter word RUBICON
I've seen this crossword clue in The Times
R
U
B
I
C
O
N
More clues leading to the result RUBICON
- Precious stone picked up, possibly blue, in Italian stream
- Polish hero the limit for Caesar?
- Polish artwork in stream Caesar crossed
- Clean what could be venerated mosaic cross here with due care
- Second river crossed in heading on — point of no return?
- Point of no return for Polish idol
- Polish figure of reverence is a cause of conflict when crossed
- Polish religious statue on river crossed by Caesar
- Polish scam to get across one ancient border
- Polish image that signifies a famous boundary
Buddy explains!

The straight part
We know that "the limit for Caesar" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case the limit for caesar = rubicon.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does RUBICON mean?
RUBICON noun- A limit that when surpassed cannot be returned from, or an action that when taken cannot be reversed.
- Especially in bezique and piquet: a score which, if not achieved by a losing player, increases the player's penalty.
- Especially in bezique and piquet: to defeat a player who has not achieved the rubicon.