Reveal: The grid answers whose clues have a number in parentheses are one letter off from being a monetary unit: 66AFRANS becomes franC, 1AEBRO = eUro, 21ABUBLE = Ruble, 57ADINAH = dinaR, 9ATALL = taEl, 70ARAID = raNd, 16AGROWN = Crown, 41ABEN = Yen. The replacement letters spell the answer: CURRENCY