You can, I think, but they might take into account that you were rejected in the first place. Bizarrely, you can't apply through clearing if you turn down your offers, so if you get rejected from a course, and accepted elsewhere, you can't then apply through clearing to that same course, but, if you applied beyond your means, it si entirely possible that you could re-allpy through clearing (having been rejected for other offers) and get in. Bizarre!