Gray has given you a good answer but note that slip up is informal. Also, I dispute that the compound noun requires a hyphen, but you'll be understood either way.

Technically, a "slip-up" (with the hyphen) is a noun. The verb "to slip up" doesn't have a hyphen. The word "slip-up" generally implies a small mistake, not a serious one, but people sometimes use it to make a big mistake sound less important.