The term 'THOSE 'AGIN' IT' refers to those who are against something, and the crossword solution for this is ANTIS (5 letters). This term is often used to describe people who are opposed to a certain idea or action, and it can be used in a variety of contexts. For example, someone might be described as an 'anti-war activist' if they are actively protesting against a war. Similarly, someone might be described as an 'anti-abortion advocate' if they are campaigning against abortion. In general, the term 'THOSE 'AGIN' IT' is used to refer to those who are against something.