Pixel Puzzles: UndeadZ

You get this achievement for killing a zombie with a trip wire during a puzzle/zombie game. Just start any puzzle by choosing it and hitting the Go button. You can buy a tripwire by choosing the right-most item in the store (the one with "FTE" on it, just like the achievement image). Place the tripwire anywhere in the killing alley. When the first zombie appears and hits it the achievement should unlock.

The image implies that this will require 5 kills, but I unlocked it after just one.