The most common and most likely answer to this crossword clue is the 7 plus 7 letter word FINDERS KEEPERS
F
I
N
D
E
R
S
K
E
E
P
E
R
S
Buddy explains!
The straight part
We know that "part of children’s code" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case part of children’s code = finders keepers.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.