A LEDGER line is a short, horizontal line used in musical notation to extend the range of notes beyond the staff. It is typically used to notate notes that are higher or lower than the normal range of the staff. The term 'LEDGER line' comes from the accounting term 'LEDGER, ' which refers to a book or other document used to record financial transactions. The ENTRY for this crossword solution is 'ENTRY, ' which is a five-letter word meaning 'the act of entering something into a record or register.'