I would spray it. If you spray it, it dies. If you mow it, it will keep coming back. If it is a nice clover plot, early maintenance can prevent problems down the road - especially in clover plantings that may persist for a number of years. Remember, with a clover/chicory plot - you cant spray Butyrac to control broadleafs or you will kill your chicory. Pure clover stands are generally easier to maintain. You also don't want to keep mowing your chicory down.