Possible Clues:

• Artery-clogging compound
• Artery-narrowing compound
• Trainer retaining Piggott — non-starter — one doesn't want too much of this
• It's unhealthy for Piggott in school, but not at first
• It's vital to body, replacing cool shelter
• Blood vessel clogging compound
• Lets her cool off — it may cause problems of the heart
• Egg yolks are high in it
• Compound affecting arteries
• Artery-clogging substance