The most common and most likely answer to this crossword clue is the 2 plus 1 plus 6 letter word DO A RUNNER
I've seen this crossword clue in The Times
D
O
A
R
U
N
N
E
R
Buddy explains!
The straight part
We know that "leave without paying" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case leave without paying = do a runner.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.