The term 'clinch up' can be solved by the crossword solutions of SEW and TIEIT. Clinching is a method of joining two pieces of material together, usually by sewing or tying. It is commonly used in the construction of clothing, bags, and other items. Sewing involves stitching two pieces of fabric together with a needle and thread. Tying involves using a knot to secure two pieces of material together. Clinching up is a way of making sure that the two pieces of material are securely joined together.