The most common and most likely answer to this crossword clue is the 6 letter word ERUPTS
E
R
U
P
T
S
More clues leading to the result ERUPTS
Buddy explains!

The straight part
We know that "goes off" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case goes off = erupts.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 ERUPTS mean?
ERUPTS verb- To eject something violently (such as lava or water, as from a volcano or geyser).
- To burst forth; to break out.
- To spontaneously release pressure or tension.