You do not need a degree but to get into the field you must have a good portfolio of sketches or photos of clothing that you designed. There is a lot of competition so you have to have a competitive advantage. A degree means that you underwent formal training and in addition to talent you will have learned various techniques for presenting your ideas and basic knowledge of fabrics and clothing manufacturing processes which are not easy to learn on your own unless you have been working as an apprentice. If you know you have the talent you should go for it because every field is always looking for fresh ideas.