Add clementine juice to a medium sauce pan and sprinkle the gelatin over it. Let it sit for 1-2 minutes. Turn the stove on, and on low heat stir in the sugar into the juice and gelatin mixture. Cook stirring for 3-5 minutes, just until all the sugar and gelatin has dissolved.
Transfer the mixture to a glass bowl and refrigerate for 30-40 minutes, or just until settled. Its important to check on the mixture every 5 minutes after 30 minutes have passed and give it a few stirs. The mixture is ready when it has a pudding texture.
Whisk the heavy whipping cream on high speed until stiff, when soft peaks have been formed, reduce the mixer speed to low and add the gelatin mixture to it. Whisk on low until combined. Make sure to scrape the walls of the bowl with a spatula, to make sure the mixture is fully combined.
Place the yellow cake into the center of a 9 inch springform pan, there will be space around it. Pour the mousse over the cake letting it fill in around the side. Refrigerate at least for 1 hour before adding the peach jelly layer.
NOTE: if you have a higher springform pan, or a cake ring, pour some of the mousse over the cake, top it with the second layer, and cover with the remaining mousse mixture.