The most common and most likely answer to this crossword clue is the 4 plus 2 plus 3 plus 6 letter word YEAR OF THE RABBIT
I've seen this crossword clue in The Guardian
Y
E
A
R
O
F
T
H
E
R
A
B
B
I
T
Buddy explains!
The straight part
We know that "New arrival/(4,2,3,6)" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case new arrival/(4,2,3,6) = year of the rabbit.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.