adderall and clen are based off the same phenylalanine base structure, and both of them are broken down in the body via similar pathways. Adderall is known as an MAOI-B, which means it will inhibit the oxidation of other compounds with amine structures (line clen) and make them stay in the body longer. The result of this is similar to stacking ephedrine and caffeine, as it will cause a lower dose of clenbuterol to be just as effective in the body.
As long as you're using adderall for studying/focusing purposes and not to get tweaked out, you should be fine. Just be careful with the dosages of both.