The belly is probably the most 'stubborn' of all the areas to lose fat from. Even after you have trimmed down all the other body parts and toned up, its still an uphill battle to get at least a little definition in the belly area.
The way fat burning works in your body is determined purely by genetics. Not by the exercise you are doing or how quickly or slowly you are doing it, but rather, your genetics, activity level (in general) and diet. As it relates to your cycling, that is a good start, but it may not be adequate enough for you. Especially if you just began, it will take a while before you start seeing any results, let alone in your belly area. I would advise you to mix it up a little. Mix some cardio, with some resistance training. Go for a jog, do some circuit training and adjust your diet for complex starches, lean protein, greens, water. Cut down everything else not in those categories (moderation is key).
Here are a few workouts that you can do to the tune of losing some weight and toning up the stubborn parts of your body.