that little clip is about the size of your thumb & is under one of the (5) holddown nuts (it slips on a stud, before the nut). sometimes the flat flange can be extremely tight on the studs & you might (gently/appropriately) pry the flat flange out a bit (evenly) to get it slightly free and first unscrew the threaded adjuster in the correct direction so there IS some play there then with the drum, slide hammer it out. the interference fit of the flat flange (the (5) holes, their fit on the studs might be what is holding things immobile rather than the bearing etc that is inside the housing