The most common and most likely answer to this crossword clue is the 5 plus 7 letter word STAGE MANAGER
I've seen this crossword clue in The Daily Telegraph
S
T
A
G
E
M
A
N
A
G
E
R
More clues leading to the result STAGE MANAGER
- Male celebrity upset by a German worker behind the scenes
- One responsible for flats and other properties?
- Theatre employee finds a celebrity reeling in shock
- Her Majesty’s production controller?
- Controller behind the scenes turning a handle during reel
- Member of theatre staff found a celebrity reeling in shock
- Theatre worker, a star that’s upcoming caught by surprise
- Surprise about a celebrity returning, one working in theatre
- East German criminal hoarding silver is the person behind the scenes
- One behind the scenes playing a strange game
Buddy explains!

The straight part
We know that "the person behind the scenes" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case the person behind the scenes = stage manager.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.