To be indentured is to be forced to work by some contract. It started out as a word for a contract between masters and apprentices. Now it describes anyone bound to work, like it or not, because of some deal.
Use the adjective indentured to describe someone who's bound or attached in a legal sense. If you're an indentured plumber's apprentice, you have guaranteed that you'll do that job in a particular way, for a specific length of time. If you're indentured to your grandmother, you may have promised to feed her cat every day for a month. When the word is used in this casual way, it implies a sense of duty that's become a burden.