The most common and most likely answer to this crossword clue is the 10 letter word IMPROPERLY
I've seen this crossword clue in The Times
I
M
P
R
O
P
E
R
L
Y
More clues leading to the result IMPROPERLY
Buddy explains!

The straight part
We know that "without justification" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case without justification = improperly.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 IMPROPERLY mean?
IMPROPERLY adverb- In an improper manner; not properly