How can one clarify orange juice to clear orange flavoured gelatine? In UK we have a small cake called a jaffa cake which has a sponge base with an orange flavoured gelatin disc covered two thirds of base (think flying saucer/UFO shape) and covered with chocolate.

I can temper chocolate and I can cook sponge.  I was wondering how they made the clear orange gelatine part.  Specifically how can one take orange juice which is opaque and arrive at an orange flavoured clear gelatin?

EDIT: 
A different way of asking is how come marmalade is clear?  I mean I know that one can make a consomme from tomato juice or beef by using egg whites which uses the albumen to filter out pulp but there must be a different technique for orange juice.

LINKS:


Bartender advice on clarifying fruit juice - suggests coffee filter (also mulls agar)
Agar clarification - agar is vegan gelatine - article suggests simmering, cheesecloth and coffee filter
Clarification Agar vs Gelatin
You might try simple agar clarification.  Dave Arnold has written extensively on the technique.  Basically, you use agar to create an orange juice gel. Once set, you use a whisk to turn the gel in to curds.  Pour into a cloth, hang, and allow to drain. Done correctly, the orange juice will be clear.  You can google the technique.  It's fairly easy and doesn't take too long.  You can then manipulate that liquid in many ways.  This is not how marmalade is made, but it will allow you to clarify almost any fruit or vegetable based juice/puree without a centrifuge.