This achievement is for completing Bonnino's Stripclub without dying on normal difficulty, it's fairly straightforward until you get to the end boss. The shotguns work well at taking his health down, and i would recommend saving grenades until you face him. The zombies throughout the level can be taken down with ease using the flame thrower. The achievement will pop after the cutscene
*Note you can start the level in normal, switch to easy once you start and then change to normal before you beat the boss*