Possible Clues:

• That sort of 13 across is faulty
• Tense, being immature
• Tense declaration of total self-esteem
• Although tense, it couldn't be better
• Even when so tense I could not be better than this
• Flawed, defective
• Was tense, but now I couldn't be better
• Tense yet apparently confident claim to flawlessness
• An egotist's self-assessment is defective
• 'Although tense, I couldn't be better (9)'