bodybuilding at 45

bodybuilding at 45
Bodybuilding?

I am 14 and have a lot of muscle but I work for muscle mass instead of the definition because I know I can not get cuts until I die my weight.I have the fat covering my muscles, except for forearm.My legs and biceps are enormous, but again, there is a layer of fat cover them.I benchpress the bar (45), 35 on each side and have a very severe chest. I need to know if I work for muscle definition? What is the job for the definition instead of mass?