The following guide has been copied and pasted from True Achievements and is my guide. I decided to post it here for anyone on PS4 who needs help earning this trophy.
I got this in Paupers Drop. The 3rd harvest spot which is right after you break through the wall made by the brute splicer. There are two adjacent staircases and a door way opposite so set trap rivets at all three entry points and also set trap rivets all the way around the body. Now hide down the side of the left staircase. You are close enough to the little sister to protect her without taking fire damage if you are lucky. Save every few seconds just in case something goes wrong. 2 or 3 splicers should come in and the trap rivets should take care of them but I was also using incinerate in the direction of the splicers on the opposite side just in case then a brute splicer comes in which is a bit tricky. He took out most of my rivets and I had no money to get any more so I stayed down the side of staircase and his rock throwing hit the bannister and protected me. I just came out every few seconds, used incinerate, hit him with rivets and bucks and he was down. All that was left was for me to pick up the little sister and the Trophy Unlocked.