keep one's nose clean


Stay out of trouble. For example, Dad told Brian to keep his nose clean from now on or he'd cut off his allowance. [Colloquial; late 1800s]

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.