The term "cleaning up on" means to make a lot of profit or succeed greatly in a particular area. The opposite of this action would be to fail or lose in that same area, so the antonyms for "cleaning up on" would be struggling, suffering losses, or falling behind. Instead of winning big, one might experience setbacks, downtrends, or even bankruptcy. The concept of antonyms shows the flip side of any expression, and in this case, it highlights the risks and uncertainty of any business venture. While "cleaning up on" can have a positive connotation, its antonyms remind us of the other side of the coin.