The most common and most likely answer to this crossword clue is the 4 plus 4 letter word ATOM BOMB
I've seen this crossword clue in Financial Times
A
T
O
M
B
O
M
B
More clues leading to the result ATOM BOMB
- A grave old doctor, one of two ending conflict
- Big weapon old doctor stored in a vault
- Such as Little Boy Blue broadcast, with catastrophic results?
- Crowd round in a crypt for Little Boy, maybe
- Grave after grave, first of two once dropped by America
- Explosive article criminal mob hid in burial place
- Weapon at disposal of one mob after another?
- Having reached zero megabytes twice, it’s very destructive
- It’s grave after a mob trashed device
- A grave order to second-grade weapon
Buddy explains!
The straight part
We know that "Big weapon" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case big weapon = atom bomb.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.