If your 6'3"at 237.....I'm pretty sure your not 15% BF unless your really jacked. I'm 6'4" and 13.5% bf and I'm 194lbs....just stating as a reference. But ether way anavar will cut you down, and a really good diet. I changed up the time I tested in between reps on my workouts and got super anal with my macros, I weighed out everything and started timing every meal to a T, and I lost 6lbs and 4.5% BF in 5 weeks. So maybe try that and anavar and cut quicker