I was a civilian stationed overseas in 2007. I had a really, really bad day under extreme stress and, long story short, ended up being cited by an MP with failure to identify. I wasn't arrested, there was just a report written and nothing else happened. I just ended up being extremely embarrassed. I'm still a civilian but now may need a secret clearance and I'm worried about this coming up. I'm assuming it will always be in my record?

Even secret clearances have different levels. I would hazard a guess that it will be on file and revealed. It shouldn't be too big a deal, depending on how much they want you for the job... tell them upfront, reported but not charged. If it's not there, and they ask you about it, don't even elaborate; just say what you said here.