Possible Clues:

• Produced a lot of revolutionary dry wine
• Crazy time around capital of Ibiza island
• Agitated air following rejection of cheese and wine
• Island's prosperity assured by militant organisation
• Island created by Gershwin
• Paid occasional visits to sierran region of Portugal
• Salaried ambassador embraces retrograde island
• Admire a new dessert wine
• 'Island' composed by Gershwin?
• Strong white cheese turned up by composer George's brother