Possible Clues:

• Amateurish painter not quite capturing northern river
• Local heading off to cut European flower
• Poor painting taking in North English river
• Flower, European, containing odd bits of blue receding
• Musically blue European river
• Flower's crude brushwork about nature's primordial energy
• It rises in the Black Forest
• River ban due for review
• River on which four national capitals are located
• It flows through four capitals