Barber's Call is a term used to describe the sound made by a barber when they are ready for their NEXT customer. It is usually a loud call or whistle that can be heard throughout the shop. The crossword solution for this term is NEXT, which is a four-letter word meaning 'immediately following in time, order, or sequence'. This term is often used in the context of a barber shop, where the barber will call out 'NEXT!' when they are ready for the NEXT customer.