Possible Clues:

• Not prepared to go to bed, yarn
• Fabric (of natural fibre)
• Soft white substance used to make fabric - in song, Old Man River don't plant it
• The Material weight of the bed
• That's the stuff that provides so much weight under the bed
• That's the stuff that gives weight to a little bed
• Study including exaggerated material
• Boll contents
• Frock fabric
• Firm rejected over the top new material