The most common and most likely answer to this crossword clue is the 4 letter word NERO
N
E
R
O
More clues leading to the result NERO
- Emperor in Wagner opera
- Fiddler supposedly with refusal to entertain the Queen
- Fiddler supposedly taking part in Wagner opera
- Somewhat insane Roman?
- Emperor found in throne room
- Northern Queen meets old emperor
- Famous fiddler never covers Queen
- Tyrant reportedly close to opposition leader
- Roman noble disheartened, retreating soldiers
- Notorious fiddler caught in headline robbery
Buddy explains!

The straight part
We know that "Emperor" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case emperor = nero.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.