(verb) to wrong-foot someone means to manipulate the situation to make an innocent person look bad, guilty. or inept. Often used by sly people to deflect the blame they deserve onto someone else, or to win a promotion at work, or to steal someone else's mate by making their rival look less desireable.
"Charlie was scamming hundreds of dollars on his expense account -- but when I pointed this out to the boss, Charlie wrong-footed me and somehow I got the blame! Unbelieveable!"
Denise knew the end of her relationship with Joe was coming when Charlene wrong-footed her, telling a party story that made it look like Denise got drunk when she hadn't...which just happens to be one of Joe's freakout points.