The most common and most likely answer to this crossword clue is the 8 letter word TELLTALE
I've seen this crossword clue in The Guardian
T
E
L
L
T
A
L
E
More clues leading to the result TELLTALE
- Swiss legend possibly revealing secrets
- Revealing falsehood suppressed by one of the Archers?
- Legendary Swiss patriot thanks the French for revealing source
- Revealing lines in a letter, sadly, Romeo erased
- Revealing backside reportedly, kiss partner first?
- Revealing Rossini’s libretto?
- Count on story being revealing
- Archer gets Troy beer — that’s revealing
- Grass could be a little taller, except for trail
- Betraying utter legend
Buddy explains!

The straight part
We know that "revealing /revealing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case revealing /revealing = telltale.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 TELLTALE mean?
TELLTALE noun- One who divulges private information with intent to hurt others.
- Tattletale; squealer.
- An indicator, such as a warning light, that serves to warn of a hazard or problem.
- Something that serves to reveal something else.
- A movable piece of ivory, lead, or other material, connected to the bellows of an organ, whose position indicates when the wind is exhausted.
- A length of yarn or ribbon attached to a sail or shroud etc to indicate the direction of the flow of the air relative to the boat.
- A mechanical attachment to the steering wheel, which, in the absence of a tiller, shows the position of the helm.
- A compass in the cabin of a vessel, usually placed where the captain can see it at all hours, and thus inform himself of the vessel's course.
- A machine or contrivance for indicating or recording something, particularly for keeping a check upon employees (factory hands, watchmen, drivers, etc.) by revealing to their employers what they have done or omitted.
- A bird, the tattler.
- A story or fable that has a moral or message.
- Revealing something, especially something not intended to be known.