The most common and most likely answer to this crossword clue is the 5 letter word ERUPT
I've seen this crossword clue in The Times
E
R
U
P
T
More clues leading to the result ERUPT
- Clean back and front of tube that’s burst
- Might broker do this with market finally 100 per cent up?
- Blow up, being rather uptight? Not entirely
- Time to clean up discharge
- Vent sudden anger, Virgin having backtracked – then fall out of train
- How teeth are said to appear to explode
- Break out flipping unadulterated drop of tequila
- Boring partner up the spout
- Break out in laughter up there
- Hamster up the trousers to burst out?
Buddy explains!

The straight part
We know that "Blow up" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case blow up = erupt.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 ERUPT mean?
ERUPT 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.