The crossword solution for the term 'VINEGAR PARTNER' is 'OIL'. OIL is a type of liquid fat that is extracted from plants and animals, and is used in many different ways. It is often used as a cooking ingredient, as a fuel source, and as a lubricant. In the context of the term 'VINEGAR PARTNER', OIL is used as a partner to vinegar, which is an acidic liquid made from fermented grapes or other fruits. Together, OIL and vinegar are commonly used as a salad dressing.