a pair of metal rings connected by a chain and fastened to a person's wrists or the bottom of their legs to prevent them from escaping

The shackles had begun to cut into his ankles. 镣铐已经开始卡进他的脚踝了。

something that prevents you from doing what you want to do

The press, once heavily censored, has managed to shake off its shackles. 新闻界一度受到严格审查，现已设法摆脱了束缚。