The most common and most likely answer to this crossword clue is the 5 letter word FOEHN
F
O
E
H
N
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 = foehn.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 FOEHN mean?
FOEHN noun- A warm dry wind blowing down the north sides of the Alps, especially in Switzerland.
- A similar katabatic wind developing on the lee side of a mountain.