From Longman Dictionary of Contemporary Englishstand up to somebody/something phrasal verbFIGHT FOR OR AGAINST somethingto refuse to accept unfair treatment from a person or organization He’ll respect you more if you stand up to him. Cliff couldn’t stand up to bullying. → stand→ See Verb table
Examples from the Corpus
stand up to • Of how the spindly high school youngster had stood up to, among others, Alonzo Mourning.• The next day a student stood up to him.• They are in no position to stand up to hostile superiors.• He and his Revolutionary Council expressed supreme confidence in their ability to stand up to the United States and its coalition partners. 