Related Clues:

• Become weary
• Lose tautness, in a way
• Falter at the finish
• Sixth word in the Pledge of Allegiance
• Calm down
• Flow out
• Yield to gravity
• Ease up
• Screenplay direction
• Lose oomph
• Emulate a tide
• Fall down
• Regress
• It appears several times in this puzzle, so fill'er up!
• Run out of steam