This achievement isn't too hard, but it is recommended that you make some progress into the story before attempting it in order to unlock better weapons, amps and overdrives.
Once you have made progress, return to the first area (Brewery) and play the Old District Night Defense Challenge.
In the pre-night defense phase, set up traps like the pyro geyser, fling boards and death by decibel around the chokeholds near the wooden barriers. Just do your best to grind above the enemies, interact with traps and use good explosive weapons like the TNTedy along with deployables like the Acid Sprinklet & Turret Copter to keep enemies away from the gate. Once they begin to break in, follow them in and use the Freeze Bomb to slow them down from getting into the final area with the vat.
If you beat the night defense challenge without losing any Overcharge (indicated on the left side of the screen), you will gain the achievement!