The most common and most likely answer to this crossword clue is the 14 letter word CONSTITUTIONAL
I've seen this crossword clue in The Sunday Telegraph
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More clues leading to the result CONSTITUTIONAL
Buddy explains!
The straight part
We know that "A healthy exercise/in accordance with principles of state" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a healthy exercise/in accordance with principles of state = constitutional.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 CONSTITUTIONAL mean?
CONSTITUTIONAL noun- A walk that is taken regularly for good health and wellbeing.
- Relating to a legal or political constitution.
- In compliance with or valid under a legal or political constitution.
- Belonging to, or inherent in, the constitution, or in the structure of body or mind.
- For the benefit of one's constitution or health.