The term 'OIL, AT A TRATTORIA' can be solved by the four-letter word 'OLIO'. OLIO is an Italian word that refers to a type of sauce or stew made from a variety of ingredients, including vegetables, beans, and meats. It is often served at trattorias, which are Italian restaurants that specialize in traditional cuisine. OLIO is also used as a term for a mixture of different types of oil, such as olive oil, sunflower oil, and other vegetable oils.