The most common and most likely answer to this crossword clue is the 7 letter word FORTUNE
I've seen this crossword clue in The Sunday Telegraph
F
O
R
T
U
N
E
More clues leading to the result FORTUNE
- A lot of money with cashier, one predicts
- Packet designed to hold air
- Strong point involving a Parisian’s large amount of money
- Appropriate to air bomb
- Large cask blocking the front part by chance
- Visionary person who counts on luck
- What may be done with tea and cookies that reveals a lot?
- Supporting, on air, people counting votes in more than one medium
- Working out four and ten — that’s a large sum
- Since bank worker is hiding strain, who knows what is going to happen?
Buddy explains!

The straight part
We know that "What may be done with tea and cookies that reveals a lot?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case what may be done with tea and cookies that reveals a lot? = fortune.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 FORTUNE mean?
FORTUNE noun- Destiny, especially favorable.
- A prediction or set of predictions about a person's future provided by a fortune teller.
- A small slip of paper with wise or vaguely prophetic words printed on it, baked into a fortune cookie.
- The arrival of something in a sudden or unexpected manner; chance; accident.
- Good luck.
- One's wealth; the amount of money one has; especially, if it is vast.
- A large amount of money.
- To happen, take place.
- To provide with a fortune.
- To presage; to tell the fortune of.