The crossword solutions for the term SOURCE OF ZEST are PEEL, RIND, and LIME. A PEEL is the outer layer of a fruit or vegetable, and it can be used to add flavor to dishes. The RIND is the hard outer layer of cheese, and it can also be used to add flavor to dishes. Lastly, limes are citrus fruits that are often used to add a zesty flavor to dishes. All three of these solutions are sources of zest that can be used to add flavor to food.