If you elucidate something, you explain it very clearly. If you don't understand fractions, a visit to the pie shop may elucidate the subject for you.
Elucidate is from Late Latin elucidare, from the Latin prefix e- "thoroughly" plus lucidus "clear, bright." This Latin adjective is the source of English lucid, which describes someone who thinks clearly or something that is clear enough to understand.
