The term 'PARTS OF GIGS' can be summarized as the components that make up a live performance. This includes the performers, the instruments, the sound equipment, and the stage setup. The four-letter solution to this crossword is 'MEGS', which stands for Musical Equipment and Gear Setup. This refers to the equipment and gear that is necessary for a successful live performance, such as microphones, amplifiers, speakers, and other sound equipment.