What is the legal standard in Islamic law for loose clothing in front of women and unmarriageable kin (mahrams)? Is it considered unlawful (haram) for slightly or significantly wide trousers to cling to the body when moving or sitting, or for a skirt to describe part of the body?

Religion is ease, and it removes hardship from the Ummah. The 'awrah of a woman in front of other women is from the navel to the knee. In front of her mahrams, it is her entire body except for what is customarily exposed, such as the limbs. It is not obligatory to wear loose clothing in front of women or mahrams, but it is prohibited to wear anything that defines the 'awrah or does not conceal it.