The term 'Core Element' can be defined as a fundamental part of something. In this case, the crossword solution for the term is SEED, which is a four-letter word. A SEED is a small embryonic plant enclosed in a covering called the SEED coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant. Seeds are the primary means by which plants reproduce and spread across the landscape.