A true one-piece takeaway is when the club, the arms, the shoulders and torso all move together smoothly to start your golf swing.  Your arms stay connected to your torso.  You want to avoid letting your arms separate from your body as you take the club away.

Imagine the triangle that your shoulders, arms and hands form at address position remain intact as you start your swing.  Your torso or core stabilize as your arms swing back. If you pick the club up too quickly, you’ll destroy the lines of the triangle and your club will veer off plane leading to flaws in the rest of the swing.