The most common and most likely answer to this crossword clue is the 5 plus 6 letter word DEPTH CHARGE
I've seen this crossword clue in The Guardian
D
E
P
T
H
C
H
A
R
G
E
More clues leading to the result DEPTH CHARGE
Buddy explains!
The straight part
We know that "a bomb" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a bomb = depth charge.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.