Clue: Sources of Riesling in Oppenheim — just any wine? (5)
Answer: RIOJA
Explanation: Definition: wine
First letters ('sources') of '**R**iesling **I**n **O**ppenheim **J**ust **A**ny', for the Spanish wine. In the surface, the Oppenheimer Krotenbrunnen vineyard is the source of the best-known Riesling wines of the area.