The phrase "a real detective" is correct and usable in written English.
It can be used to emphasize the authenticity or professionalism of someone in the role of a detective, often in contrast to amateur or fictional portrayals.
Example: "Unlike the characters in the movies, a real detective must gather evidence meticulously and follow strict protocols."
Alternatives: "an actual detective" or "a genuine detective".
He willingly discussed his days as a real detective, particularly how the experience informs his on-screen detecting (though he pointedly mentioned that in a career with dozens of roles, only "about 10" have been cops).
You have to be a real detective and follow his trail.
Not only that: Loomis had a real detective story to tell.
Richard Feynman – The Fantastic Mr Feynman (BBC2, Sunday) – was also a real detective of sorts.
She will often spend weekends investigating with her friend Carol, a real detective, asking people if they know anything about the crime.
By Jill Lepore Charlie Chan, based on a real detective with the Honolulu Police, became best known through Warner Oland's portrayal.
There are numerous other true sentences like this, such as "Sherlock Holmes is more famous than any real detective", etc., all of which appear to involve real relations between existent objects and nonexistent ones, but whose Russellian paraphrases are false.
It is also a future where the police's job is little more than to watch the latent criminals they control because if they did any real detective work, they might start to think like the criminals they are trying to catch and thus become latent criminals themselves".
His gun, it turned out, was a toy that looked real, Detective Delpozo said.
The court also heard that Mehajer had impersonated Police Detective Sergeant Matthew Taylor in a fake email to himself only for the real Detective Taylor to discover a copy of it on his phone.
A quirky hunt for the real detective.
