NFL's Clinton Portis -- I'M NOT BROKE ... Money Issues Stem from 'Bad Business Deal'

Clinton Portis says he didn't blow his entire NFL fortune -- even though he reportedly owes more than $1 million to creditors -- claiming his money issues stem from a bad business deal but he's still "doing fine."

The long story short ... Portis says he's still dealing with the financial fallout from a bad investment deal in 2008 ... where he sank a ton of cash into a casino that ultimately went bankrupt.

Portis -- along with several other former NFL players -- later sued a financial adviser who allegedly duped them into investing in the first place.

"This been ongoing since 2011, 2012 ... we just gotta go thru the court process," Portis tells us. "There's nothing else I can do. My lawyers are currently dealing with this."

Portis continues ... "At the time I was the biggest name and had the deepest pockets. Now, they're trying to hold me solely responsible for what was a bad business deal involving a lot of different people."

Now, Portis reportedly owes more than $1 million to various creditors -- including $450k in taxes, $287k to the MGM Grand in Vegas and has other issues with real estate and car loans.

"My lawyers are on top of it," Portis says ... "I'm still eating. Look at my Instagram. I'm not starving. I'm gaining weight."