If you cut the wrong piece in Dressmaker, select the unwanted cut piece and use Recycle from the side menu. Then cut the correct pattern piece from your fabric. This is the documented way to deal with a wrong cut; it is more useful than restarting the whole commission.
Check the piece before cutting again
Hover over a pattern piece to see its name and where it belongs on the mannequin. The mannequin's left is on your right, so a left or right piece can be easy to confuse. Place the new piece along the fabric grain if you want the best quality.
If you meant tissue or a pattern layout rather than a cut fabric piece, first identify what is selected in the cutting room. The available guides describe recycling wrong cut pieces from the side menu; they do not establish a separate tissue recycling command.
For the complete order of play, use the beginner tutorial. If the dress is already assembled, see how to finish and deliver it.
Sources: Into Indie Games walkthrough, Guidexon beginner's guide.