Possible Clues:

• Staple of classic rock, informally
• A Marx Brother almost landed on river, going west in balloon
• It used to go right up, up the river at last
• One of the Marx brothers briefly hovers over river, going up in aircraft
• Early German airship
• Old craft, given variable energy, flower power doubled up
• The Hindenburg, e.g.
• Eponymous German aeronaut
• For a germ, an enormous floater (8)
• Dirigible count?