Open Question: Is it possible to do cardio and still tone?

I'm 5'7 girl, muscular, average, athletic frame. I go the gym alot but i have overdone the muscle coz i did number 9 on the cross trainer but have recently switched it down to 4/5 so i don't gain anymore muscle, my theighs are extemely muscley and i hate that coz its manish so now like i said i'm focusing on number 4/5 on the cross trainer and also very light weights, i turn 18 this october so i wanna loose a couple stone by then. I go the gym 5, sometimes 6 days a week and have started a healthy diet today. I am a sporty girl and i wanna be a personal trainer when i'm abit older so i like learning stuff like this, but please don't give me akward answers coz i do know how to exercise i just need to know this simple question in one sentence >>> Is it possibly to do cardio and still tone? Thanks :)