The term 'Site of Activity' can be represented by two crossword solutions: FRONTLINE (9 letters) and HIVE (4 letters). FRONTLINE is a term used to describe the most active or intense part of a situation, such as a battlefront in a war. HIVE is a term used to describe a place where a large number of people or animals live and work together, such as a bee HIVE. Both terms can be used to describe a place where activity is taking place.