The fear of wearing too tight of clothes, or over-constricting attire. This irrational fear could be due to a variety of reasons including the desire to conform to an urban dress code, or simply due to a low body image.
Jenny: Man, Richie sags his pants constantly! Look at how ghetto he is!
Billy: Yeah, man, he's totally got clothestrophobia. I have never seen him wear proper fitting jeans!
That feeling of utter discomfort one feels when s/he wears clothes that are too small/tight for her/him.
Suzanne, make sure you have clothes that fit right before you go to the party. You don't want to get clothestrophobia there!