you probably planted the throw and grow too thick and ryegrass out competed the brassicas and clover in the mix.
One option would be to plant a mix of clover and oats. The oats pop up real quick but will die at the first freeze, by then the clover should be starting to come on good. In my experience you don't get a lot of forage with clover the first season it is planted. It is slow to get established. When planted in the fall you really don't start getting good forage until the following spring. That is why i like to start a clover plot with a nurse plant such as oats, wheat, or like William said rye.
good luck---but you are correct--clover makes a great plant for a small killing plot.
todd