Related Clues:
- Have the backbone
- Brave, turning up the radio a bit
- Bold venture
- Challenge from the radicals rebuffed
- Exhibit audacity
- Instigation for a prank, often
- Impetus for a bungee jump, maybe
- 'Don't you ___!'
- Challenge revolutionary retailer advertising clothes
- Risk it
- Incentive for a stunt, perhaps
- Challenge "accepted" by 20-, 36- and 50-Across
- Offer up a challenge
- Challenge to do something foolhardy
- Increase what is at stake ... or a hint to answering 20-, 30- and 46-Across