Bring wine to simmer in small saucepan. Add saffron. Remove from heat. Cover; let stand 15 minutes.
Heat 1 tablespoon of the oil in heavy large saucepan over medium-high heat. Add leeks and onion; saute until tender, about 8 minutes. Add garlic; saute 1 minute. Add stock, tomatoes with their juices, oregano and saffron mixture. Simmer 20 minutes. Add sausage, mussels and clams. Cover; boil until shellfish open, about 8 minutes (discard any that do not open).
Meanwhile, dip 1 side of fish in cornmeal. Sprinkle with salt and pepper. Heat remaining 2 tablespoons of oil in heavy large nonstick skillet over high heat. Add fish, cornmeal side down, and cook until bottom is golden, about 4 minutes. Turn fish over. Ladle 1 cup of soup over. Cover and simmer until fish is just cooked through, about 4 minutes.
Transfer fish, cornmeal side up, to 4 shallow bowls. Arrange clams, mussels and sausage around fish. Top with remaining soup. Sprinkle with parsley.