How tall are you? How much do you weigh? This will take lots of hard work and commitment! You might end up changing your lifestyle... for the better! Either that or you'll get that six pack, then revert to your old eating habits and then regain that fat... Your decision!
You most likely have some body fat covering your abs. That said, you need to get rid of that body fat.
How do you get rid of body fat, you ask?
Calorie deficit!
Basically you need to burn more calories than you are taking in. This requires that you calculate your daily maintenance caloric intake (I forgot how you do this, whoops!), then chop off about 500 calories per day.
You also need to clean up your daily diet. This means you need to do away with sweets, fried foods, fast foods, white bread, white anything, etc... Read around in
this forum for GREAT information on dieting advice.
Once that is done, you need to assess your cardiovascular training. You "do a bit of running and cycling". What does that mean? How often do you run? Cycle?
I suggest trying high intensity interval training in the form of walk-backs. What you do is: sprint for 15 seconds, then walk back to where you started. Then sprint again for 15 seconds, then walk back to where you started again. Do this SEVEN times for the first week, then add an additional cycle per each following week. Do this two to four times a week.
Also, in order to have a famed six pack, you need to have abs. Everyone has them, but working them out won't hurt anything and will help define them. There's a really nice video floating around on these boards called "8 Minute Abs." I've been following this video for the past two days and my abs are burning (which doesn't happen all that often).