The most common and most likely answer to this crossword clue is the 5 letter word SPARK
I've seen this crossword clue in The Daily Telegraph
S
P
A
R
K
Buddy explains!

The straight part
We know that "Writer Muriel" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case writer muriel = spark.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.
What does SPARK mean?
SPARK noun- A small particle of glowing matter, either molten or on fire.
- A short or small burst of electrical discharge.
- A small, shining body, or transient light; a sparkle.
- A small amount of something, such as an idea or romantic affection, that has the potential to become something greater, just as a spark can start a fire.
- Any of various lycaenid butterflies of the Indomalayan genus Sinthusa.
- (in plural sparks but treated as a singular) A ship's radio operator.
- An electrician.
- To trigger, kindle into activity (an argument, etc).
- To light; to kindle.
- To give off a spark or sparks.
- Appalachian To court.
- A gallant; a foppish young man.
- A beau, lover.
- To woo, court; to act the gallant or beau.