Well, it's really more of a situational fetish, like ENF (embarrassed nude female). Put simply, it's an umbrella term used to describe any situation where there is a fully clothed female and a fully nude (or at least functionally nude) male.
''What happens'' is not fixed, anything that can lead to, happen in, or result from that situation is possible for the setting. For example, if a male streaker encounters a clothed female jogger. Any situation where a male is nude around a female who is not would count.
This fetish and its opposite tend to play off the embarrassment or humiliation of the situation depending on setup. You can always check the tag on a hentai manga site if you want examples.
