The most common and most likely answer to this crossword clue is the 12 letter word DISOBEDIENCE
I've seen this crossword clue in The Daily Telegraph
D
I
S
O
B
E
D
I
E
N
C
E
More clues leading to the result DISOBEDIENCE
Buddy explains!
The straight part
We know that "problem in the earliest garden" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case problem in the earliest garden = disobedience.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 DISOBEDIENCE mean?
DISOBEDIENCE noun- Refusal to obey.