Welcome aBoard, DD. I ran your description through Onelook's reverse dictionary, and came up with nothing that seemed appropriate. My thought is, then, that it's likely some variation on the words sly or tricky will have to suffice.
Main Entry: sly
Part of Speech: adjective
Definition: clever, devious
Synonyms: arch, artful, astute, bluffing, cagey, calculating, canny, captious, conniving, covert, crafty, crooked, cunning, deceitful, deceptive, delusive, designing, dishonest, dishonorable, dissembling, double-dealing, elusive, foxy, furtive, guileful, illusory, impish, ingenious, insidious, intriguing, mean, mischievous, plotting, roguish, scheming, secret, sharp, shifty, shrewd, slick, smart, smooth, sneaking, stealthy, subtle, traitorous, treacherous, tricky, underhand, unscrupulous, wily
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