Answer to Meta Crossword #5

The meta answer is 25. (The hint was: Find the 2-digit number that comes next in a sequence hidden in the grid.)

Explanation: The starred clues have answers arranged in pairs: FORMULA / LINER, CONNECT / SCORE, CLOUD / INNINGS and SWEET / CANDLES (see grid below). The puzzle’s title, “Square in the Middle,” suggests the answer involves squares in the middle of each pair. The hint—that a number completes a hidden sequence —also suggests that the square is numerical in nature, like a square number (e.g., the result of multiplying a number by itself. Example: 10×10=100, so 100 is a square number).

But which square numbers? Ones that form well-known phrases when added to the words in each pair:

FORMULA [1] LINER = Formula 1 / one-liner
CONNECT [4] SCORE = Connect Four / four score
CLOUD [9] INNINGS = cloud 9 / nine innings
SWEET [16] CANDLES = Sweet 16 / Sixteen Candles

1 (=1×1), 4 (=2×2), 9 (=3×3), and 16 (=4×4) are all consecutive square numbers. The next one in the sequence is 25 (=5×5), the meta answer.