Preheat oven to 180 degrees C. Grease baking trays.
In a large bowl, cream together margarine and brown sugar. Beat in egg and mashed banana, then stir in vanilla. Combine flour, bicarb soda, salt, cinnamon and cloves; stir into the banana mixture. Mix in rolled oats and walnuts. Drop by rounded spoonfuls onto prepared baking trays. Leave room for spreading.
Bake for 8 to 10 minutes in preheated oven. Allow biscuits to cool on baking trays for 5 minutes before transferring to a wire rack to cool completely.