Very neatly cut the rhubarb into 5cm lengths, then cut each length into neat batons, about the size of thick matchsticks, and set aside.
Tip the sugar, vanilla pod and seeds, wine and lemon zest into a wide pan and pour over 800ml cold water. Give everything a good stir to dissolve the sugar slightly, then set over a medium heat and gradually bring to boil, stirring occasionally. Turn up the heat to high so the syrup is boiling really fast, then turn off the heat and immediately stir in the rhubarb. Cover the pan with a plate or lid and leave to cool completely, then pour off 350ml of the syrup and reserve. Chill the remaining rhubarb and syrup.
Soak the gelatine in cold water. Heat the reserved syrup in a small pan, then turn off the heat. Gently lift out the gelatine, give it a squeeze, then add it to the pan to dissolve in the syrup. Pour into 6 serving bowls, then put in the fridge and leave to set overnight.
To serve, gently break up the jelly a little in each bowl, give the rhubarb a good stir, then use a slotted spoon to spoon an even layer of rhubarb into each bowl. Pour over some of the syrup and place a spoonful of clotted cream in the middle of each bowl to serve.