Bit of Q.E.D.

ERAT

Think of the Latin phrase that often concludes a mathematical proof.

"Bit of Q.E.D." is a clever way to hint at the last letters of the phrase. "Q.E.D." stands for the Latin "quod erat demonstrandum" (meaning "which was to be shown"), often used at the end of proofs. The clue asks for a "bit" of it—so you take the last letters of each word: quod (D), erat (T), demonstrandum (M) would give DTM, but here it’s simplified to just the last word’s ending, "erat," shortened to "ERAT." The answer plays on extracting a fragment from the full phrase.