if thats the clean out screw you are talking about, its highly worthless and I dont even bother removing mine for cleaning.
If you do want to get it out and its super tight, you'll need to boil a pot of water and stick that end of the barrel into there and let it sit for a bit before trying to remove it with your screw driver.
Keep a small hammer on hand as well. If you can't get it to break loose, sometimes giving the screw driver a few helpful taps with the hammer while applying pressure in the direction to remove the screw, will help it break loose. Just like using a slap hammer.
