I remember seeing this when I was really young, sometime between 1985-1989 but the show itself could be older of course as I know this was just something that was on TV.
I remember a boy thinking there was a monster in his closet. His mother of course doesn't believe him. I don't remember a father figure in this story but there might have been. The short ends with the boy going off to school, so it is daytime, and the mother goes to his room to clean it. She is picking up some toys, maybe like a fake brick or large Lego or something, so she is on her knees and like halfway in his closet just cleaning up and there it is. A monster, and it gets her, the end.
I remember this being so terrifying because it got her during the day, it wasn't your typical monster in the night thing and that just really stuck with me. I have checked every episode of all the standard 80's horror shows that had new episodes of the week and have come up with nothing. But honestly it feels like this was a very short story, even shorter than your typical 80's horror story of the week formula.