Possible Clues:

• Tim, Ivan (anag)
• Essential element of diet
• Natural organic substance essential to health
• French wine -- drinking it before noon can provide what your body needs
• A vain imposter? Creative prose wasted, perhaps
• A, B, C, D, E, or K
• Riboflavin, e.g
• One A Day product
• Substance essential in small quantities to normal metabolism
• 'A', for instance may be six-time African despot