Possible Clues:

• Composer: unit of his work given to most important piece
• Composer of a measure of music — tons, certainly
• Composer is a 'Sir', all right?
• Hungarian composer (1881-1945)
• Lionel, fine as a composer
• He wrote Bluebeard's Castle and Bartholomew Fair
• Simpson - decent composer
• Small ship's restricting to composer
• Composer Béla interested in folk music
• Bela . . . . . ., Hungarian composer