This achievement requires you to attach an arc mine to a rat, and for it to then be triggered by an enemy who is killed by it. Arc Mines are similar to the Spring Razors in the main game, but they disintegrate enemies instead of just killing them.
The first place you will find arc mines, is in the barracks in the yard of the Rothwild Slaughterhouse in the very first level. You will find some workers who are being held prisoner in this area and they will ask you to set them free and tell you where the key is, the key is in the same room as the mines.
A great place to actually get the achievement in this level (though I'm sure there are countless opportunities) is right at the end of the level, when you are told to meet up with
Billie Lurk. Small spoilers follow.
Billie has been caught by a group of Overseers, one with a music box. On the ground right behind the music box Overseer, is a rat. I killed the music box Overseer with an arrow, then jumped down when the other Overseers were facing the opposite direction, placed a mine on the rat and waited to be spotted. As soon as an Overseer began to run at me, he was disintegrated.