The Highlands instrument referred to in the crossword solution is bagpipes, which is an 8-letter word. Bagpipes are a type of musical instrument that originated in Scotland and are still widely used in traditional Scottish music. They consist of a bag filled with air, a chanter, and several drones. The chanter produces the melody while the drones provide a continuous harmonic accompaniment. Bagpipes have been used for centuries in Scotland and other parts of the world, and they remain a popular instrument today.