Related Clues:

• Bug, to so speak
• Perfection spoiler
• It might be only a scratch
• Dent or scratch
• Diamond defect
• Diamond imperfection
• Scratch on a gem, e.g.
• Design ___
• Achilles heel
• Fault
• Scratch on a diamond, e.g.
• Shortcoming
• Design problem
• It may be tragic
• Chink in the armor, say