Possible Clues:

• Resilient one in crumbling castle
• Narrow strip of rubber
• Cats lie in order to be able to spring
• Springing back to shape after stretching
• Feature of laciest pants?
• It stretches lace and it's in need of adjustment
• Resilient one in derelict castle
• Stretchy lace - it's woven in a new way
• Stretching to the end if 16 across in ice
• If it's in ice, it will not go bad for a stretch