The most common and most likely answer to this crossword clue is the 3 plus 7 letter word RUN THROUGH
I've seen this crossword clue in The Times
R
U
N
T
H
R
O
U
G
H
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 = run through.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 RUN THROUGH mean?
RUN THROUGH noun- A rehearsal of a drama, especially an uninterrupted one, but with no makeup or costume
- A brief outline of the main points of something; a rundown
- In which trains continue without stopping while going through a station.