The term 'tighten, perhaps' can be solved in two ways in a crossword puzzle. The first solution is 'relace' which is a 6 letter word. This means to replace the laces of a shoe or other item. The second solution is 'retie' which is a 5 letter word. This means to tie something again, such as a shoelace or a knot. Both solutions refer to the idea of tightening something, either by replacing it or by tying it again.