I used to have a six-pack but now all I have is a little lump and I need to lose fat, not weight.?

It's not a huge little bit of fat, I can feel the muscle underneath it, but I can't go to the gym or anything like that because I'm a lot younger than this website thinks I am. I can't control my own diet yet because I still live with my mom :3 I'm just a kid... but the only sport I do was soccer but even that is gone now because it's summer. I used to do swimming, soccer, karate, and baseball but all those I stopped because Middle School started last year and I had a lot to keep up with. I play Alto Saxophone, Tenor Saxophone, Viola, Guitar, and Piano. The only instruments I don't have private lessons for are Guitar and Tenor Saxophone so I'm still pretty busy, so doing anything that takes more than 60 minutes a day is out of the question, but now that it's summer, I have a lot of time on my hands but I intend to stick to the exercise routine throughout the next school year so it can't be too long. so please help! I need to lose fat! I'm not saying I need to lose weight because I only weigh 80 lbs.