This one's pretty easy: just be up front about it.
"I had an idea. I went out on my own to try it out. It didn't work out, but I learned a lot along the way."
Then just be prepared to talk a little about the things you learned, and how they helped you grow as a professional.
No employer worth working for is going to ding you for taking a risk like that -- even outside SV! Seriously! -- as long as you can make it clear that you really were working on something during that period, rather than sitting on the couch eating Cheetos.
Honestly, if you told me that, I'd want to know more; it would not be a black mark (or even grey). I'd consider that to be a high marker for initiative and hackerishness.
I would, however, be concerned that you'd take off as soon as you found a VC to buy into your idea and give you a few years of runway. So you'd have to alleviate that concern (within reason, of course).
"I worked on a mobile startup, right before iOS got big; J2ME games. Yeah, I think we sold maybe 50 games once? Anyways, stayed in college, no harm done."
"I tried a startup. After a year, it imploded in not-quite-glorious fashion. Still dealing with the fallout from that, but I learned a lot about business and product development."
There's no shame in failing, and anybody worth working with will appreciate your experience--that is, if you learned anything.
"I had an idea. I went out on my own to try it out. It didn't work out, but I learned a lot along the way."
Then just be prepared to talk a little about the things you learned, and how they helped you grow as a professional.
No employer worth working for is going to ding you for taking a risk like that -- even outside SV! Seriously! -- as long as you can make it clear that you really were working on something during that period, rather than sitting on the couch eating Cheetos.