Serve with raw oysters and clams on the half shell.
Sprinkle gelatin over 2 tablespoons water in a small bowl; let stand until gelatin has softened, about 5 minutes.
Using a vegetable peeler, remove thin strips of zest from 3 lemons. Squeeze enough juice from zested lemons to yield 6 tablespoons plus 1 teaspoon; set zest and juice aside. Cut remaining lemon into thin rounds; reserve for garnish.
Bring wine and 2 tablespoons water almost to a boil in a small saucepan over medium-high heat. Remove from heat, and add lemon zest; let steep 15 minutes. Pour mixture through a fine sieve into a medium bowl; discard solids. Add gelatin mixture, and stir until dissolved.
Stir in sugar, salt, and vinegar. Let cool completely. Stir in 5 tablespoons lemon juice. Cover; refrigerate until jelled, 6 hours (or overnight). Before serving, stir in remaining 4 teaspoons lemon juice. Serve garnished with lemon rounds.