The most common and most likely answer to this crossword clue is the 6 letter word RESIZE
I've seen this crossword clue in The Times
R
E
S
I
Z
E
Buddy explains!
The straight part
We know that "to change in scale" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case to change in scale = resize.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 RESIZE mean?
RESIZE noun- An operation that changes the size of something.
- To alter the size of something.
- To change in size.