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"sneaky" is also used as a crossword clue. If that's what you saw, the answer is often underhand (9 letters).
Definitions
Secretive or deceptive in a quiet, careful way.
Word origin
From sneak + -y.
Used in a sentence
“Catching those thieves will be hard: they're so sneaky!”
“Be sneaky. Fish frighten easily.”
“Some fans may have mistaken the album’s floatiness for aimlessness, but Mr. Mercer’s songs have never been sneakier, or prettier.”
Source: Wiktionary, CC BY-SA 4.0
Used as a crossword answer1 curated clues
01“Secretive and sly”6 letters
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