There’s no fast way to get a clearance. The shortest route would be to get an unarmed security job. Most security positions require at least a tier 1 background investigation which can get you to secret. The other way would be to find a job that requires one.. Most secret clearances take about 60 days so if you don’t have a clearance now, you’re in for at least 60 days.
I’ve had a tier 5 clearance for 30 years, my first investigation took 18 months. Today they can get tier 5’s done in 6-12 months… so that’s a long time.
Bottom line, there are only 2 ways: 1) You get a contractor job at a government agency that requires only a secret clearance, or 2) You get an armed/unarmed security officer job. Other than the aforementioned only federal government agencies require clearances ie Confidential, Secret, Top Secret, TS/SCI. Most other jobs dealing with corporate entities and NGO’s require public trust, that is banks, hotel staff, casinos, law firms, HVAC..not for profits, humanitarian organizations etc..
BTW.. DSS (Defense Security Service) has a 1yr backlog.