Sexual selection is a “special case” of natural selection.... Sexual selection acts on an organism’s ability to obtain (often by any means necessary!) or successfully copulate with a mate.
The ability to find a mate to reproduce with is the selective pressure!
Sexual selection is even powerful enough to produce features that are harmful to the individual’s survival. For example, extravagant and colorful tail feathers or loud mating songs are likely to attract predators as well as interested members of the opposite sex.