The most common and most likely answer to this crossword clue is the 5 plus 6 letter word COMIC RELIEF
I've seen this crossword clue in The Times
C
O
M
I
C
R
E
L
I
E
F
Buddy explains!
The straight part
We know that "Break from tension caused by cracks?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case break from tension caused by cracks? = comic relief.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.