In this page you can find a detailed description of "Clean Job" achievement that you can unlock in Get Even. You get this trophy for infiltrating the building where Jasper is imprisoned without raising an alarm.
Warning - If you were detected and you alarmed enemies you don't have to replay the entire level. You can simply select the option to load the last checkpoint and replay only the most recent part of the memory.
You can get this trophy during "Jasper's Dying Minutes" memory that is reserved for Black. You must be stealthy from the beginning of the level.
The first few mercenaries are near the starting point. Try to alarm them "slightly" so their status becomes yellow and they start to look around the area. Then, you can use this chance and sneak to the next location (creating a hole in a wall by scanning an anomaly) or wait for a perfect moment and eliminate them silently (use a silenced pistol or perform executions when you are right behind their back).
When you go through the hole in the wall you find yourself in a big area that surrounds the warehouse. Because of the size of this location the game gives you more freedom (in addition to that you can find anomalies and create new obstacles). If you want to eliminate enemies then you should rely on a silenced pistol again or approach the enemies and perform silent executions on them (start with the guard that went to urinate). Otherwise, you must use the map regularly and walk around your enemies or wait until they start patrolling other areas. The last thing to do is to select any of the entrances that allows you to enter the building.
The last location in which you must be stealthy is the big warehouse presented in the picture above. Right after you enter the building you should focus on the stairs on the left, the ones that can take you to the upper balconies. Be sure that no one is going in Black's direction and start walking on the balconies (while crouching) and reach the opposite end of the warehouse.
You don't have to hurry with leaving this location because soon one of the guards can start patrolling. It is recommended to start sneaking behind him. Then, you can get closer to him and eliminate the guard silently or hide somewhere and wait until he turns back and goes to the place where he was initially standing.
Your goal is to reach the exit presented in the picture, located in the far right corner of the building. Fortunately, after using this path you won't encounter any enemies. Reach the cell with the hostage. The trophy should be unlocked shortly after you scan him and go to the next area (it will happen right before you enter the room with columns and the phone that must be scanned).