The most common and most likely answer to this crossword clue is the 9 letter word NUTSHELLS
I've seen this crossword clue in The Times
N
U
T
S
H
E
L
L
S
Buddy explains!
The straight part
We know that "Cases one’s crackers to tackle" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cases one’s crackers to tackle = nutshells.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 NUTSHELLS mean?
NUTSHELLS noun- The shell that surrounds the kernel of a nut.
- A short book summarizing an area of law.