Answered by Shaykh Yusuf Weltch
Is it permissible for a women to wear a loose skirt or trousers that are a few inches above the ankle in length and cover the remaining part of the leg with thick opaque tights or socks?
In the Name of Allah, the Most Merciful and Compassionate
Yes, it is permissible for her to wear a loose skirt or trousers that cover the majority of her legs, as long as the remainder of her legs are covered. Socks and/or thick tights suffice in covering the rest of the leg. [Ibn ‘Abidin, Radd al-Muhtar]
The minimum amount of covering for the validity of prayer is that the skin of all places obligatory to cover must be covered such that the skin cannot be seen. [Ibid.]
Tightness, however, is prohibitively disliked, if the shape of the body is clearly visible. If the shape is only slightly discernible it is somewhat disliked, yet not sinful. [Ibid.]
Difficult to Maintain Covering
Certain areas, the covering of which, are deemed difficult to maintain. Areas such as, just below the chin, just above the wrists, and just above the ankles are among this category. [Ibid.]
Although these areas are obligatory to cover, they are somewhat overlooked due to the difficulty and constant upkeep needed to keep them covered. [Ibid.]
In this regard, if the entire body is properly covered with loose garments but the last portions just before the ankle are covered with slightly tighter clothing this may also be overlooked in the absence of easier alternatives.
Hope this helps
Allah knows best
[Shaykh] Yusuf Weltch
Checked and Approved by Shaykh Faraz Rabbani