A corset is an undergarment worn by some women to enhance the shape of their body. It is made stiff by whalebone or some other stiff material, and it is tightened by having the laces pulled. Remember Scarlett O'Hara's tiny waist? She achieved such a small middle by wearing a corset and having the laces pulled extremely tight.
Would your character be willing to go to such extremes to have a tiny waist? Does your character long to be physically attractive to men so badly that she would live in discomfort and risk her health and well-being by wearing a tight Victorian corset? Suffering for Beauty - the Victorian Corset