Clockwork refers to the inner workings of mechanical timepieces such as clocks or pocket watches. It could also describe another organism of similar reliability.
In 2268, when Spock suggested that if the landing party disbelieved in the illusions of the Melkotian planet, it could not harm them,Leonard McCoy replied, "We (humans) don't have that clockwork ticker in our head like you do" (i.e. can't just turn off their feelings.) (TOS: "Spectre of the Gun")
In 2365, Jean-Luc Picard described the universe as having "clockwork perfection". (TNG: "Where Silence Has Lease")
In 2366, Paul Stubbs noted that over and over again, the intense gravitational pull of a little neutron star, inside an unnamed binary star system in the Kavis Alpha sector, sucked up star material from its neighboring red giant which built up on the surface until it exploded every 196 years like clockwork. (TNG: "Evolution")