There is a hormone that can be traced in your urine when you are pregnant, and that is called the HCG hormone. Advanced pregnancy tests can detect this hormone & what percentage of the HCG hormone that is in your urine.
Clear urine simply means that you have drank extra water or fluid, and then it came out in your pee. It's actually healthier to have clearer urine, not dark or yellow. Being pregnant should not change the color of your urine, and clear urine does not indicate whether or not you are pregnant.