For Strauss, every philosopher at all times is in the situation of political persecution, and hence has to construct a specific way of writing, which on its surface is “exoteric,” that is, meant for the general, unsophisticated reader, yet is “esoteric” in its hidden message, accessible only to few “thoughtful” and “careful” readers capable of understanding the true message of and behind a text by “reading between the lines”. True philosophers, then, including Plato, “must conceal their opinions from all but philosophers, either by limiting themselves to oral instruction of a carefully selected group of pupils, or by writing about the most important subject by means of ‘brief indication’”.
source
Dmitri Nikulin, "Plato: Testimonia et Fragmenta" in The other Plato : the Tübingen interpretation of Plato’s inner-academic teachings edited by Dmitri Nikulin