Right, so Foolish is your definition, pointing to stupid or silly. Now, the numbers here are a bit sneaky — they're not sums, they're cross-references, so "1" points you to the answer at 1 across and "9" points you to the answer at 9 down. But actually the wordplay just wants the digits themselves: AS (meaning "like") followed by I (the Roman numeral for 1) followed by NINE (the number 9 spelled out), building up AS-I-NINE.