The most common and most likely answer to this crossword clue is the 6 letter word SPRITE
I've seen this crossword clue in The Times
S
P
R
I
T
E
More clues leading to the result SPRITE
- Supernatural being tormented priest
- Brownie hurt crossing river
- Muddled priest showing little spirit
- Fairy Queen’s involved in malice
- Fairy godmother’s back after prince enters scene
- Changing sitrep displayed by movable icon
- Hob, say, priest needed for cooking
- Ill feeling scoffing first bit of repulsive brownie
- Priest abused drink
- Spirit put out with a dash of Ribena added
Buddy explains!

The straight part
We know that "Mythological entity" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case mythological entity = sprite.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 SPRITE mean?
SPRITE noun- Spirit; mind; soul; state of mind; mood.
- A supernatural being; a spirit; a shade; an apparition; a ghost.
- A kind of short arrow.
- A spirit; a soul; a shade
- An apparition; ghost
- An elf; a fairy; a goblin.
- The green woodpecker, or yaffle.
- A two-dimensional image or animation that is integrated into a larger scene.
- An electrical discharge that occurs high above the cumulonimbus cloud of an active thunderstorm.
- A spayed female ferret.