The most common and most likely answer to this crossword clue is the 5 letter word FABLE
I've seen this crossword clue in The Daily Telegraph
F
A
B
L
E
More clues leading to the result FABLE
- Story in super French article
- Great, extremely labyrinthine story
- It isn’t true it comes to a moral conclusion
- Muscle appearing in revolutionary fairy tale
- Sort of a bleeding heart story
- Fellow’s clever story
- Force accomplished account
- Material to lie on
- Story in book abridged in another leaf
- Heartless line ending great story
Buddy explains!

The straight part
We know that "It isn’t true it comes to a moral conclusion" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it isn’t true it comes to a moral conclusion = fable.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 FABLE mean?
FABLE noun- A fictitious narrative intended to enforce some useful truth or precept, usually with animals, etc. as characters; an apologue. Prototypically, Aesop's Fables.
- Any story told to excite wonder; common talk; the theme of talk.
- Fiction; untruth; falsehood.
- The plot, story, or connected series of events forming the subject of an epic or dramatic poem.
- To compose fables; hence, to write or speak fiction; to write or utter what is not true.
- To make up; to devise, and speak of, as true or real; to tell of falsely; to recount in the form of a fable.