Related Clues:

• Sink in the middle
• Become weary
• Lose tautness, in a way
• Yield to gravity
• Lose oomph
• Fall down
• It appears several times in this puzzle, so fill'er up!
• Tire
• Give a little
• Drop down
• Perceptive
• Sofa problem
• Downturn
• Grow weary
• Hang loosely