clear one's name
Also, clear oneself. Prove someone (or oneself) innocent. For example, She not only wanted to be acquitted, she wanted to clear her name entirely. This locution employs the verb clear in the sense of “purify” or “wash away a stain.” [Late 1400s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.