Possible Clues:

• Guilt
• Reliable evidence originally provided by policeman establishes guilt
• Endeavour to hold up reptile by its extremities: it may bite
• Sorrow for sin or wrong-doing
• Pity about son being taken in again
• Regret over Rome's destruction
• Some err, possibly, showing shame
• Compunction concerning titbit left to go off
• Guilty conscience about mouthful not finished
• Regret theorem — or sentiment framing it