The most common and most likely answer to this crossword clue is the 9 letter word RURALISES
I've seen this crossword clue in The Daily Telegraph
R
U
R
A
L
I
S
E
S
More clues leading to the result RURALISES
Buddy explains!
The straight part
We know that "leaves the big city behind" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case leaves the big city behind = ruralises.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 RURALISES mean?
RURALISES verb- To make rural.
- To become rural; to rusticate.