The most common and most likely answer to this crossword clue is the 7 letter word RUSTLER
I've seen this crossword clue in Financial Times
R
U
S
T
L
E
R
More clues leading to the result RUSTLER
- One stocktaking?
- Does he make swishing sounds when stealing cattle?
- Sovereign holds good man to be lawbreaker
- One who makes a whooshing sound stealing cattle
- He’s kept busy stocktaking
- Dodgy stocktaker, one noisily thumbing through papers?
- One standing on leaf? Tea leaf?
- Thief who can be heard going through papers
- Bad result beginning to rock one taking stock
- Thief starts right but gets wrong result
Buddy explains!

The straight part
We know that "lawbreaker" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case lawbreaker = rustler.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 RUSTLER mean?
RUSTLER noun- One who rustles; a cattle (or other livestock) thief.
- A bovine animal that can care for itself in any circumstances.
- (Western US) An alert, energetic, driving person.
- That which makes a rustling noise.