A Secret is actually very easy to obtain. Basically it's a test to whether or not you're going to tell the truth on your application and if what you are in involved in is going to cause enough damage to potentially harm the government in someway or can be used as blackmail against you (hence harm the gov by you flipping sides).

It is possible being on the registry may hurt you as it will probably cause you to be seen as a habitual drug user but maybe not. Whatever you do, don't try to hide it. Maybe downplay the heck outta it, but don't hide it. Hopefully you have kept it on the downlow with friends, neighbors and co-workers that you're a mmj patient. If you have, you should be alright. If a lot of others know you partake, it might be some headache for you.

When I first joined the military, my job required a TS (top secret), so I had to go through all the crap. I told the truth that I had smoke mj a few times, but that was it (again - stretching the truth a bit, but as long as it can't be proved it's safe). They interviewed my friends, family, co-workers, former co-workers, high school classmates, college roommates, etc, etc, etc.... They dug out people who I hadn't hear from in years, so even in prison on drug charges. As far as I know, they never found anyone who said they had smoked with, had seen me smoke nor have they seen me under the influence.

It took a while, but I finally got my clearance (first time is the longest, renewals are pretty straightforward) BUT for the first five years in the military somehow I was always selected for the supposedly "RANDOM" piss test. Luckily I was smart enough to completely stop and was pissing my own pure clean urine. Oh by the way, the fed piss test is monitored - there will be another person watching you very closely!)It was uncomfortable the first couple of times, and even made it a bit difficult to "perform on command" with someone staring over my shoulder, but after that I didn't care who it was watching me.

As a civilian working for the fed, you probably won't have to piss test very often but you may have to go to extremes to cover your enjoyment. Definitely will have to enjoy in solitude.

Good Luck! If you have more questions feel free to ask. I might be able to shed more light.

Oh I should add a Secret usually only takes a couple of month to obtain. Usually they issue an interim Secret if an initial review comes back clean (background & credit check). Bad credit is really really frowned upon as it has been the number one reason why people have sold their countries out - for money to pay gambling & credit card debt!