Possible Clues:

• Fail to get a job done
• Fail on a field?
• Fumble
• *Make a mistake ... and what the answers to the starred clues do, in two ways?
• Mess up ... and a hint to 17-, 24-, 36- and 50-Across
• Blow it
• Mishandle a situation
• Fail to follow through like a major leaguer
• Make an error
• Muff