How much fuel do you carry?
My Company Ops Manual while not actually defining 'contingency fuel' describes it as compensating for:
-deviations of an individual a/c from expected fuel consumption data
-deviations from forecast met conditions
-deviations from planned routeings/cruising FLs.
No mention of holding. As I understand it, if I consider it likely that I will have to go into the hold on arrival I need to consider taking extra fuel and leave the contingency element out of the calculation completely.