probably "amazingly beautiful"

"Wondrous" is an old, antiquated word that means about the same thing as "wonderful" or "wonderfully." "Fair" is an antiquated word that can mean "beautiful." So "wondrous fair" means "wonderfully beautiful." The word order, "vision glorious" is unnatural in modern English. We would say "glorious vision." This, too, is old-fashioned, literary, or poetic English.