Possible Clues:

• Like 13-Across music
• Thin, piping
• Sounding like a bassoon
• Like marshes or bagpipes
• High-sounding buck returns unknown
• Like 11-Down
• Wanting lots of food -- no good being very thin!
• Like woodwind instruments
• Eating a lot but shunning starter to get thin
• Like Bunter losing head, becoming weak and thin?