Bring the bat down, clean and true, angled topwards but vertically horizontally. Aim to strike the ball while moving into a stationary position.
A good forward defensive stroke will be soft-yet-firm, played late at the earliest opportunity with supple hands that caress the bat handle in a vice-like grip using only the fingertips.
Played correctly, you will get a shimmer of atonal somnolence from the willow. This is a sign that you have NOT played the shot correctly. Continue practising.