The most common and most likely answer to this crossword clue is the 4 plus 9 letter word LIVE CARTRIDGE
I've seen this crossword clue in The Daily Telegraph
L
I
V
E
C
A
R
T
R
I
D
G
E
Buddy explains!
The straight part
We know that "charge in case" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case charge in case = live cartridge.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.