How is “go deep” used?

In Spotlight (2015), one line is: “We don't want the Herald going deep on this.”

Which movie is “go deep” from?

The clip at the top of this page is from Spotlight (2015).

We don't want the Herald going deep on this.

8 作品で登場 · 1 本目

to extend, reach, or move a long way downward or inward

13 本の映画に登場

編集映画の 83%
to extend, reach, or move a long way downward or inward
lts legs go deep underground.

定義：Oxford Advanced Learner's Dictionary 第 9 版