Bicycle Mechanics - Troubles in 5th Gear...

It's a 1993 Ross Professional Gran Tour. It's a great steel bike after I've played around with it. But I can't figure out what's wrong with 5th Gear!

It only happens in 5th gear, never happens any other time. Whenever I get into 5th gear and start pedaling harder, the bike kinda juts. It doesn't happen all the time but just usually when I'm accelerating. It's a pretty hard jut, whenever I'm over the pedals and it juts I nearly fall over the handlebars. It's not something that's preventing me from riding, but it is preventing the bike from being perfect. Anyone have a clue what could be going on? My first guess is that it's hitting the front derailleur or something but I don't know for sure.

Thanks for any help guys.

Definition of "Jut":


bulge: something that bulges out or is protuberant or projects from its surroundings; "the gun in his pocket made an obvious bulge"; "the hump of a camel"; "he stood on the rocky prominence"; "the occipital protuberance was well developed"; "the bony excrescence between its horns"
stick out: extend out or project in space; "His sharp nose jutted out"; "A single rock sticks out from the cliff"
protrusion: the act of projecting out from something

I can't make any of these definitions work in this context. Please restate.

I'm guessing you mean it skips.

You need a new freewheel and chain. They wear together, and your smallest sprocket wears faster than the others.

What's 5th gear ?, these are not car transmissions.