thicken stew with excess floating fat
If you want to use the fat to keep the flavor, or because you are keeping a diet where fat is considered more beneficial than carbohydrates, there are several ways. 

First, you can skim the fat, make a roux with the skimmed fat, then add it back. 

Second, you can skim the fat, add a little bit of broth and an emulsifier, whisk until you have a nice thick emulsion, then add it back. 

If you use a straciatella style thickening, the fat eyes will frequently disappear between the rags, especially if you can get them to break up very small. 

But if you are asking because you want to save some work, I don't think there is a good way. Generally, if you use enough flour or other starches at the frying at the start of the stew (including tomato pastes and such), the fat will bind with the starch instead of floating. But it seems that your recipe is for a thin stew, and the fat continues to float there.