A clockwork toy or device has machinery inside it which makes it move or operate when it is wound up with a key.
a clockwork train set.
一套带发条装置的玩具火车。
like clockwork
If you say that something happens like clockwork, you mean that it happens without any problems or delays, or happens regularly.
The president's trip is arranged to go like clockwork, everything pre-planned to the minute.
总统的行程安排得极其周密,每一件事情都预先计划,时间安排精确到了分钟。