Possible Clues:

• What's left is wet; keep it under control
• What's left is wet, so keep it back
• Engineers make a strong effort to check
• Put in a straitjacket, e.g.
• What's left is wet. Control it
• Tie up - arrest
• Holiday shower under bar
• What's left seems to be wet. Check it
• Hold back a holiday, with bad weather coming
• Remainder of the water, bottle up