The most common and most likely answer to this crossword clue is the 5 plus 6 letter word STAGE FRIGHT
I've seen this crossword clue in The Sunday Telegraph
S
T
A
G
E
F
R
I
G
H
T
More clues leading to the result STAGE FRIGHT
- Fellow in house left causing actor to stop performing
- Problem with public address speakers
- Arrange contest, admitting Rocky’s initial reluctance to go on
- Leg fractured originally: justifiable concern for player
- Fear operating in theatre?
- Ongoing panic
- At first, egg husband to sort out performance anxiety
- 50s movie with great fights, suspenseful
- The first gag could be what unnerves performer
- Player’s nerves level following remedy
Buddy explains!
The straight part
We know that "Fear operating in theatre" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fear operating in theatre = stage fright.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.