The most common and most likely answer to this crossword clue is the 4 letter word PERP
I've seen this crossword clue in The Times
P
E
R
P
More clues leading to the result PERP
Buddy explains!
The straight part
We know that "criminal in US" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case criminal in us = perp.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 PERP mean?
PERP noun- (law enforcement) Perpetrator.
- At or forming a right angle (to something).
- Exactly upright; extending in a straight line toward the centre of the earth, etc.
- Independent of or irrelevant to each other; orthogonal.