A winding device is a mechanical tool used to store energy in the form of tension. The two crossword solutions for this term are STEM, which is a four-letter word, and SPOOL, which is a five-letter word. A STEM is a cylindrical object that is used to hold a SPOOL, which is a round object with a hollow center used to store and dispense wire, thread, or other materials. Together, these two components make up a winding device.