Combine cranberries, brown sugar and walnuts together. Spread the mixture into the bottom of the prepared pie shell. Beat eggs well; Gradually add the sugar; continue beating. Stir in flour and melted butter. Pour batter over the berries in the pie shell. Cover edges of pie crust with foil and bake at 400 degrees for 15 minutes. reduce heat to 350 degrees; remove foil and bake 35 minutes longer. Serve with ice cream.