as a personal trainer i have to say this has been the biggest area of frustration to me. it is impossible to "spot reduce" fat off any one area of the body. we are genetically predisposed to carry our fat stores in certain areas. the first place it goes on is likely to be the last place it comes off.
muscle tissue and fat tissue have a completely different makeup. you can no sooner turn fat into muscle than you can turn a pillow into an apple. you can do abdominal work everyday until you are exhausted but that will only give you fabulous abdominal muscles UNDERNEATH the fat that lies on top of it. the only approach that works is 3 pronged:
an excellent eating plan
consistant cardiovascular work
the biggest benefit to strength is that the more muscle you have the better your ability to burn calories. muscle is a very metabolic tissue. it has been estimated that 1 pound of muscle burns between 30-50 calories a day....even at rest! in a typical male your age, you can expect to gain 8 pounds of muscle in your first 3 months of crossfit!
i must repeat...as i do nearly every week at the gym:
you can not work one muscle in such a way as to reduce the fat that lies on top of it. it is an overall cumulative effect of doing everything right.
i hope this is not disappointing. happy crossfitting.