The most common and most likely answer to this crossword clue is the 1 plus 6 plus 3 plus 3 plus 6 letter word A CHANGE FOR THE BETTER
I've seen this crossword clue in Independent
A
C
H
A
N
G
E
F
O
R
T
H
E
B
E
T
T
E
R
Buddy explains!
The straight part
We know that "Revised gambling regulations/an improvement" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case revised gambling regulations/an improvement = a change for the better.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.