Removal of portions of or the entire clitoris is called female circumcision or female genital mutilation. It makes it very difficult if not impossible for women to have orgasms and is usually performed on pre-pubescent girls. FGM is primarily a social practice, not a religious one. Female genital mutilation predated Islam. It originated in Africa and remains today a mainly African cultural practice.
Here is a link to a good article on FGM.