Possible Clues:

• A major, now - at university, a lieutenant
• Imago-stage insect
• A chaperon is usually one
• Like some content aimed at teenagers
• Stallion, e.g.
• Minor supervisor
• At least 18 heads of Academies denounced unsatisfactory, lazy teachers
• Endlessly boring time had by a responsible person
• Not for children
• Young ___ (literary category)