As Smooth as a __ = Quiet, Calm
This page is the CodyCross answer for the clue below from Casino, Group 272, Puzzle 3 (Online Casinos).
Question is: As Smooth as a __ = Quiet, Calm
and the answer is: MILLPOND
Word Meaning:
MILLPOND — A pond or reservoir produced by damming a river or stream in order to provide a steady source of water for a millrace.
Definitions from Wiktionary.