Straighten, in a way, can be accomplished by using the crossword solutions of UNCOIL, uncross, UNCURL, and UNBEND. UNCOIL is to unwind or loosen something that has been wound or coiled up, such as a rope or cable. Uncross is to undo something that has been crossed, such as two lines that have been crossed over each other. UNCURL is to straighten something that has been curled, such as a piece of paper or a strand of hair. UNBEND is to make something straight that has been bent, such as a wire or a pipe. All of these words refer to the action of straightening something in some way.