The NRSV's rendering is typical of many translations. It takes τί as "what" and seeing an object already there for ἀκούω, renders the whole thing with a what-cleft.Luke 16:2 wrote:καὶ φωνήσας αὐτὸν εἶπεν αὐτῷ · τί τοῦτο ἀκούω περὶ σοὺ; ...
So he summoned him and said to him, ‘What is this that I hear about you? ... (NIV)
On the other hand, if τί is adverbial, it would mean something like "Why do I hear this about you?" But this is not a popular choice.
The context isn't too helpful, unfortunately, for this is a rhetorical question and we don't have dishonest steward's answer.
Any objections for an adverbial τί here?
(PS. ἀκούω here is another so-called "perfective present," see v.1 καὶ οὗτος διεβλήθη αὐτῷ.)