Here's how I learned to make gravy, many years ago. Skim off the fat and dregs (or use a bit of butter) into a skillet. Add a bit of flour (maybe a tablespoon, depending upon how much gravy you're making) and stir over medium heat, until the flour is browned. At this point, the mixture will be a bit crumbly looking. SLOWLY add a bit of the broth, a LITTLE at a time. At first, only about a tablespoon, at a time. STIR the heck out of the mixture, with each little addition of broth. The trick is to not introduce too much liquid, at a time. Don't be in a hurry or you'll have lumps.