The most common and most likely answer to this crossword clue is the 4 letter word HUFF
I've seen this crossword clue in The Daily Telegraph
H
U
F
F
More clues leading to the result HUFF
Buddy explains!

The straight part
We know that "Blow" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case blow = huff.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 HUFF mean?
HUFF noun- A heavy breath; a grunt or sigh.
- An expression of anger, annoyance, disgust, etc.
- One swelled with a false sense of importance or value; a boaster.
- To breathe heavily.
- To say in a huffy manner.
- To enlarge; to swell up.
- To bluster or swell with anger, arrogance, or pride; to storm; to take offense.
- To treat with arrogance and insolence; to chide or rebuke rudely; to bully, to hector.
- To inhale psychoactive inhalants.
- (draughts) To remove an opponent's piece as a forfeit for deliberately not taking a piece (often signalled by blowing on it).