Here is the full list of all 16 Clandestinity of Elsie achievements.
You finally found Elsie.
Return to Burnie's Garage.
Enter the sewers (again).
Kill a Thorn.
Leave the sewage plant.
Diverted the water flow.
Kill an Alchy.
Escape the Singed ambush.
Gather medical supplies at the hospital.
Kill 10 Singed.
Find the pendant.
Find the Blood Bag at the Troy Restaurant.
Activate the elevator at the Yorkshire Apartments.
Kill a Victim.
Save your game for the first time.
Went to the Cunningham home.