Possible Clues:

• Slim — watery
• That might be thought to be one spare king
• Carrying little fat
• Narrow and short object
• Like a poor argument
• Most of article is flimsy and unconvincing
• Weak, as a plot
• It would be thought to be such a spare king (4)
• Such a king would be thought not to be overweight( 4)
• (Of smile) weak, forced