The most common and most likely answer to this crossword clue is the 4 letter word WARY
I've seen this crossword clue in The Guardian
W
A
R
Y
More clues leading to the result WARY
- Cautious in conflict, coming to enemy finally
- Cautious fighting by Dempsey, ultimately
- Cautious course across river
- Cautious passage around river
- Cautious of danger of route across river
- Cautious and tired, losing energy
- Cautious movement of ship over river
- Cautious with Ray drunk
- Cautious manner restrains king
- Guarded last of booty after battle
Buddy explains!

The straight part
We know that "Cautious" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cautious = wary.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 WARY mean?
WARY adjective- Cautious of danger; carefully watching and guarding against deception, trickery, and dangers; suspiciously prudent
- Characterized by caution; guarded; careful; on one's guard
- Thrifty, provident