The most common and most likely answer to this crossword clue is the 7 letter word GUARDED
I've seen this crossword clue in The Daily Telegraph
G
U
A
R
D
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D
More clues leading to the result GUARDED
Buddy explains!

The straight part
We know that "Wary" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case wary = guarded.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 GUARDED mean?
GUARDED verb- To protect from danger; to secure against surprise, attack, or injury; to keep in safety; to defend.
- To keep watch over, in order to prevent escape or restrain from acts of violence, or the like.
- To watch by way of caution or defense; to be caution; to be in a state or position of defense or safety.
- To protect the edge of, especially with an ornamental border; hence, to face or ornament with lists, laces, etc.
- To fasten by binding; to gird.
- Cautious; restrained.
- Watched over; supervised.
- Not favourable.