The most common and most likely answer to this crossword clue is the 8 plus 7 letter word CARDINAL VIRTUES
I've seen this crossword clue in The Sunday Telegraph
C
A
R
D
I
N
A
L
V
I
R
T
U
E
S
Buddy explains!
The straight part
We know that "Justice and three others" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case justice and three others = cardinal virtues.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.