Dinner jelly is a type of dessert made from gelatin, fruit, and sugar. The three crossword solutions for the term dinner jelly are Sterno (6 letters), Guava (5 letters), and AGAR (4 letters). Sterno is a brand of canned cooking fuel that is used to heat up food. Guava is a tropical fruit that is often used in jellies and jams. AGAR is a type of gelatin derived from seaweed that is used as a thickening agent in many desserts.