Related Clues:

• 'Don't give up!'
• Crack, so to speak
• Essay
• Challenge
• Encouraging word
• Litmus is one kind
• Venture
• Probation
• See 31-Across
• Trial run
• Inconvenience
• Trial
• Do one's darnedest
• Entrance requirement, maybe
• With 24-Down, self-diagnosis aids