The crossword solution for the term 'Cause of a Stinging Breakup' is 'TEARGAS', which is an acronym for 'Tear Gas'. Tear gas is a chemical weapon that is used to disperse crowds or subdue individuals by causing irritation to the eyes, skin, and lungs. It is often used by law enforcement to control riots or protests. In this context, it could be used to describe the intense emotions that can accompany a breakup.