The most common and most likely answer to this crossword clue is the 11 letter word REVERBERATE
I've seen this crossword clue in The Daily Telegraph
R
E
V
E
R
B
E
R
A
T
E
More clues leading to the result REVERBERATE
Buddy explains!

The straight part
We know that "boom" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case boom = reverberate.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 REVERBERATE mean?
REVERBERATE verb- To ring or sound with many echos.
- To have a lasting effect.
- To repeatedly return.
- To return or send back; to repel or drive back; to echo, as sound; to reflect, as light, as light or heat.
- To send or force back; to repel from side to side.
- To fuse by reverberated heat.
- To rebound or recoil.
- To shine or reflect (from a surface, etc.).
- To shine or glow (on something) with reflected light.
- Reverberant
- Driven back, as sound; reflected.