"Man trap" could go one of two ways.
Or - man trap as in the sexist version. The monster posed as a youthful pretty girl to entrap Mr. Redshirt (whose name I forget if it was ever given) and then as a youthful Nancy to try to entrap McCoy. In that case, it was "a woman seeking to entrap a man."
It was a sexist time, on a show run by... well, Gene Roddenberry.