i dont get it =.=why did the kid get into the grandfather's clock???
No idea, we need an expert.
I think there could be two possibilities. First, there might be a well-known image of kid sleeping in a big clock in Japanese culture. (I doubt it, though) Second, just a meaningless image like kids hiding in a refridge. In the manga, the kid couldn't sleep with excitement, and later, he was curious about the clock, so he might have tried getting into the clock for fun and fallen asleep in the clock while playing that trick. I said it's meaningless because this manga's goal is describing the bucolic, rural atmosphere with calm tone, and the kid's sleeping in the clock is just a small event which is possible with playful kids. Not a serious and meaningful event.