### Clue: Stagger up after exercise class with advanced high-protein snack? (7)
### Answer: PEANUTS 
 ### Explanation: Definition: high-protein snack
 **Reversal of**(… up, in a down clue) STUN(to stagger/to shock) **placed under**(after, in a down clue) [PE(abbrev. for "physical education"/a period in school for physical exercises) **plus**(with) A(abbrev. for "advanced")].
Defn: Snack food containing a higher proportion of protein than other nuts.