The term YO-YO, ESSENTIALLY can be broken down into two parts: the word 'yo-yo' and the word 'ESSENTIALLY.' The word 'yo-yo' is a toy consisting of an axle connected to two disks, which is wound up with string and then released to spin rapidly around the axle. The word 'ESSENTIALLY' means fundamentally or basically. Therefore, the crossword solution for the term YO-YO, ESSENTIALLY is SPOOL, which is a cylindrical object used to store and dispense items such as thread, yarn, wire, or film.