Possible Clues:

• It's far from calming to emphasise the possibility of flu
• Taxing is trouble for most of the fuel
• Demanding headmistress fully content
• Demanding type of test for fuelless energy
• Loves escaping from stores, so foul and mentally draining
• Accent's on ample detailed testing
• Full of tension
• Left USSR wrongly supporting Soviet leader? That's worrying!
• Worrying
• Causing mental or emotional strain