The most common and most likely answer to this crossword clue is the 7 letter word REFORMS
I've seen this crossword clue in The Guardian
R
E
F
O
R
M
S
More clues leading to the result REFORMS
Buddy explains!
The straight part
We know that "turns over a new leaf" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case turns over a new leaf = reforms.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 REFORMS mean?
REFORMS noun- The change of something that is defective, broken, inefficient or otherwise negative, in order to correct or improve it
- To put into a new and improved form or condition; to restore to a former good state, or bring from bad to good; to change from worse to better
- To return to a good state; to amend or correct one's own character or habits
- To form again or in a new configuration.