This is no different for societies without clocks. I’m pretty certain that aboriginal people still living in their ancient ways don’t just stop individually to eat. They eat together (very likely after finishing a hunt). It’s not tied to the clock but it’s also very much not just “feeling hungry”. Eating is generally a social activity.

The clock is just a convenient way to get a group of people to agree what “eating time” is. They would do the same without.