Clue: Doctors gather in auditorium besieged by students? Dummies! (10)
Answer: NUMBSKULLS
Explanation: Doctors gather in auditorium besieged by students? Dummies! (10)


**MBs** (Bachelors of Medicine, so "doctors") + homophone [*in auditorium*] of **CULL** ("gather"), *besieged by* **NUS** (National Union of "Students")