Possible Clues:

• Prematurely
• Question following an insensitive joke
• "That may never be funny"
• "Don't joke about that yet"
• 'Are we not joking about that yet?'
• Question after a tasteless joke
• Response to a joke about Whitney Houston's death, perhaps
• 'Don't joke about that yet'
• Earlier than desired
• Not 16 Across, perhaps