The most common and most likely answer to this crossword clue is the 6 letter word PACKED
I've seen this crossword clue in Financial Times
P
A
C
K
E
D
Buddy explains!
The straight part
We know that "Prepared case" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case prepared case = packed.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 PACKED mean?
PACKED verb- (physical) To put or bring things together in a limited or confined space, especially for storage or transport.
- (social) To cheat.
- To load with a pack
- To load; to encumber.
- To move, send or carry.
- To block a shot, especially in basketball.
- (of the forwards in a rugby team) To play together cohesively, specially with reference to their technique in the scrum.
- (of a drag king, transman, etc.) To wear a prosthetic penis inside one’s trousers for better verisimilitude.
- Put into a package.
- Filled with a large number or large quantity of something.
- Filled to capacity with people.