This episode's headline: Forbidden Fruit; A Matter of Ethics; Considering the Cabinet. The guests include DR. FRANK YOUNG, Food And Drug Administration; AMB. MALCOLM WILKEY, Ethics Commission Chairman; FRED WERTHEIMER, Common Cause; REP. DICK CHENEY, Secretary of Defense-Designate; CORRESPONDENT: JUDY WOODRUFF. Byline: In Washington: JAMES LEHRER; In New York: CHARLAYNE HUNTER- GAULT