Related Clues:

• Slip
• Deteriorate
• Decline
• Turn bad
• Go downhill
• Leave for the winter, say
• Exacerbate
• Opposite of 'improve'
• Deteriorate, slangily
• Go up on the Saffir-Simpson scale
• Take a turn for the worse
• Migrate, maybe
• Deteriorate for owners
• That's what's being a better is likely to do for one
• Start to tank