Mixer isn't designed to “clean” coins. Some centralized services even reject coins from mixers.
Clean coins are those you get directly from mining or staking rewards, or you buy from them. However, I don’t know if there is a dedicated market for that out there.
I know that, I need to get clean coins for my eth from tornado cash that is now marked as mixer by aml checkers. What service can I use to get clean usdt?