The term 'Subject of Interest' can be defined as a topic or area of study that is of particular importance to an individual. In this case, the crossword solutions for the term are 'DEBT' and 'TBOND'. DEBT is a four-letter word that refers to money owed by one party to another. TBOND is a five-letter word that stands for Treasury Bond, which is a DEBT security issued by the United States government. Treasury Bonds are typically used as a safe investment option and are backed by the full faith and credit of the US government.