clock·work 
/ˈklɑ:kˌwɚk/ noun
/ˈklɑ:kˌwɚk/ noun [noncount] 1 : the system of moving wheels inside something (such as a clock or an old-fashioned toy) that makes its parts move
▪ the clockwork inside a mechanical toy soldier 2 — used to describe something that happens or works in a very regular and exact way ▪ Every morning, like clockwork, customers line up outside the front door of the bakery. ▪ Their wedding went (off) like clockwork. [=their wedding went very smoothly; everything in the wedding happened the way they planned] ▪ The birds return each year, (as) regular as clockwork. — often used before another noun ▪ The work was done with clockwork precision. ▪ They return with clockwork regularity. ▪ a clockwork operation
▪ the clockwork inside a mechanical toy soldier
