Jameis Winston -- I'm Ready to Model ... I Just Gotta Drop a Few Pounds (VIDEO)

Jameis Winston says he's ready to hit the runway ... telling TMZ Sports he's down for a second career in modeling -- but he'll have to shed a few lbs first!

Winston was at the Madden Live party in San Fran Thursday night -- when we asked about his recent Instagram pic that looked like it coulda been an audition for a GQ cover.

Jameis is pretty funny in the clip -- saying his GF, Breion, is the real hero 'cause she took the pic -- but noting that he's REALLY DOWN to pose for pay ... noting, "I'm very dapper!"

Winston also says he's interested in acting -- and even has a message for one of the most powerful guys in Hollywood ... LeBron James.