As stated, you have to kill 10 players , that have their shovel out, in a game.
This means that you can kill them with guns, but they have to be holding their shovel in order for it to count.
Make a game (with bots) , preferably with 9 players, and a time frame of 10 minutes. The map doesn't matter, as you can use any gun available. Keep targeting players with their shovels out, and before you know it, you'll get the achievement