The term 'GROUP CORE' can be broken down into two words, 'GROUP' and 'CORE'. The word 'GROUP' is defined as a number of people or things that are located, gathered, or classed together. The word 'CORE' is defined as the central or innermost part of something. Together, the term 'GROUP CORE' can be interpreted as a GROUP of people or things that form the central or innermost part of something. The crossword solution for this term is 'CADRE', which is defined as a small GROUP of people specially trained for a particular purpose or profession. Therefore, the term 'GROUP CORE' can be interpreted as a small GROUP of people or things that form the central or innermost part of something.