Possible Clues:

• Drummer's follow-up to a joke
• Drummer's punchline follow-up
• Drum sound after a one-liner
• Response to a joke
• Percussive punctuation for a joke
• 'Ba-dum-tss'
• Drum sound that follows a joke
• Drum stroke after a punchline ... or a hint to interpreting the starred clues' answers
• Sound after a one-liner
• Punchline drum hit