The Greek does not have calls for.
The NASB gives a more literal translation: “Here [is] the mind which has wisdom.” The passage does not intend to call upon the reader to find wisdom (or perhaps find a man with wisdom) so as to be able to understand the preceding material. It says instead that John is in the presence of a mind that has (the needed) wisdom. That mind is the angel; he is endowed with the heavenly insight needed to explain to John what this beast is all about—which he will proceed to do in the following verses.
9 This calls for a mind with wisdom: the seven heads are seven mountains on which the woman is seated;