Oddly, given the fact they are created inside the Thorian, each Clone emerges dressed in the brownish uniform common to all commandos, and armed with a shotgun.
The Clones were created from Shiala, a powerful biotic who followed Matriarch Benezia and later Saren Arterius, after she fell under indoctrination and joined his cause. Shiala was given to the Thorian as part of a trade Saren made with the creature, in exchange for the Prothean Cipher. Shiala melded with the Thorian to gain the Cipher, and then remained part of it until Shepard confronted the Thorian and freed her.
The Clones' best talent is their powerful biotics, which can knock squad members over and leave them vulnerable to the Thorian Creepers' acid attack. A Clone's shotgun can be lethal on higher difficulty settings and they also have robust shields. Using cover is important to avoid the biotic attacks. Neural Shock and Warp work quite nicely to get past the Clones' shields and prevent them from using their biotics, while Sabotage will help take out the shotgun. Because of the structure of the building, if a Clone is close to the edge of the platform, a strong enough Throw will knock her off for an instant kill. The same works for Shepard, so it'll be better to stay away from the edges.