get (one's) hands dirty
1. To do hard work, often manual labor. There is nothing more rewarding to me than getting my hands dirty in my garden. I really appreciate you guys getting your hands dirty and helping us move.
2. To be involved in something illegal or unseemly. Uncle Pete has been avoiding us ever since we discovered that he gets his hands dirty working for the mob. No one can know about my police record—I don't want people to think that I still get my hands dirty.