The most common and most likely answer to this crossword clue is the 12 letter word TRANSITIONAL
I've seen this crossword clue in The Times
T
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More clues leading to the result TRANSITIONAL
Buddy explains!

The straight part
We know that "with changes afoot" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case with changes afoot = transitional.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 TRANSITIONAL mean?
TRANSITIONAL adjective- Of, or relating to a transition
- Temporary; pending the implementation of something new