Islam requires Muslims to act upon the commandments of Shariah and shun the things that are prohibited by it. Every Muslim is enjoined to abide by it in whatever field he/she may be. It is desirable to choose a field through which one can serve the Islamic cause. It is also ordered by Shariah to earn Halal livelihood. And, in order to earn Halal livelihood trading and business is not bad but it has been appreciated and truthful businessman has been praised in Hadiths. Therefore, the same field you are studying, you can choose as your field/sector of work provided you abide by all the rulings of Shariah and do not go against its commandments.
Allah (Subhana Wa Ta’ala) knows Best
Darul Uloom Deoband