To get this achievement, you must complete the first 10 waves of horde on any difficulty. You do not need to do this on one sitting, and you do not need to do it all on one map.
You should not aim for this achievement as it will unlock on your way to one of:
Hoard the Horde
Trial by, and on, Fire
Skeletons in your Closet
I suggest if you are planning to go to level 50, then security is the best map as the bunker area surrounded by lasers is a very good defensive position.
I also suggest grabbing a friend to help you do this so that you have room for error.