The clock in one of the machines in idle tower builder
The clock is a very very expensive machine in idle tower builder. it costs 50 000 000 science.
As science is very hard to get and you can normally not get much more science then 3 million science/second without playing the game for ages, not all players have got the clock. This is totally normal and anyway even if you dont have the clock its not that bad because you need about 1 000 000 000 000 science to get the clock only to level 60.
As with all objekts, if you have got 25 billion science (25 000 000 science) you can watch an ad to get the clock for free. but you need 25 billion science and even this is not easy to get.
The clocks function is to speed up time even more if you use a time boost 19% more per 10 levels.
The best thing to do with the clock is eighter: not buy it at all and just ignore it (but it isnt such a good option)
Or just level up the clock with ads i know ads are boring but normally ads arent longer then 5 seconds and to level up the clock with science takes hours to get this much science ;-)