The most common and most likely answer to this crossword clue is the 7 letter word DIVULGE
I've seen this crossword clue in Independent
D
I
V
U
L
G
E
Buddy explains!

The straight part
We know that "Reveal" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case reveal = divulge.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 DIVULGE mean?
DIVULGE verb- To make public or known; to communicate to the public; to tell (information, especially a secret) so that it may become generally known
- To indicate publicly; to proclaim.