clock ‧ work /ˈklɒk-wɜːk $ ˈklɑːk-wɜːrk/ BrE AmE noun [uncountable]
1 . British English clockwork toys, trains, soldiers etc have machinery inside them that makes them move when you turn a key:
mechanical toys powered by clockwork
The tape was driven by a clockwork motor.
2 . go/run like clockwork to happen in exactly the way you had planned:
The concert went like clockwork.
3 . like clockwork ( also (as) regular as clockwork ) happening at the same time and in the same way every time:
Matt came round each Friday, regular as clockwork.
4 . with clockwork precision/accuracy in an extremely exact way