Avoid circularity. Since the primary purpose of a dictionary is to inform the reader what words mean, anything that absolutely denies the reader the opportunity to find out the meaning of a word he has looked up is the most serious defect a dictionary can have. Mind you, circularity does not just make things difficult - it makes them impossible. No amount of diligence on the part of the reader can penetrate the barrier of circularity.
From the Michaelis, "Moderno Dicionário da Língua Portuguesa":
despachoI guess the editors of the Michaelis didn't read Landau, then.
sm (der regressiva de despachar) 1 Ação de despachar.
(provençal despachar) vtd 1 Pôr despacho em, deferindo ou indeferindo: Despachar uma petição.