The most common and most likely answer to this crossword clue is the 5 letter word TROMP
T
R
O
M
P
Buddy explains!

The straight part
We know that "blast" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case blast = tromp.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 TROMP mean?
TROMP verb- To tread heavily, especially to crush underfoot.
- To utterly defeat an opponent.
- A blowing apparatus in which air, drawn into the upper part of a vertical tube through side holes by a stream of water within, is carried down with the water into a box or chamber below which it is led to a furnace.