Clue: Powerful Chinese nationalists rule out getting security devices (11)
Answer: STRONGBOXES
Explanation: Definition: security devices 
**STRONG** (powerful) + **BOXE**(r)**S** (Chinese nationalists with **R**(ule) "out") 
The Boxer Rebellion was a rebellion by Chinese nationalists known as *Yihetuan*, who became known as *Boxers* in English due to the martial arts they used.