You can fix greasy brown gravy by skimming the excess fat off the top with a spoon or using a paper towel to absorb it. Also, try adding a slice of bread to the gravy for a few seconds—it'll soak up some of the grease. Hope this helps!
I’ve been there! One trick that works for me is letting the gravy sit for a minute, then skimming off the extra grease with a spoon. You can also drop in an ice cube—the fat will cling to it, making it easier to remove. If you're in a rush, a paper towel lightly pressed on top can soak up some of the grease. Hope that helps!