come clean with (someone) about (something)
To admit something to someone, often regarding a wrongdoing that one has tried to hide. We have to come clean with the police about what we did before Joe gets punished for our crime! The kids finally came clean with me about eating the cookies I'd made for the bake sale.
come clean (with someone) (about something)
in. to admit (something) to someone. You’re gonna have to come clean eventually.