"BACKUPPLAN" IS THE Answer TO THE FOLLOWING CROSSWORDS

1. "just in case" strategy, and a hint to a hidden letter sequence in 17-, 24-, 37- and 52-across
2. It's often labeled "b"
3. 'just in case' strategy
4. Safety option
5. Safety net of a sort and a literal feature of 17- 23- 39- and 52-across

OTHER CLUES

1. Brush up again
2. Bête noire
3. Abecedarian
4. Ace's specialty
5. Annul, as a legal order
6. Big productions
7. Base coats
8. Author ayn