The most common and most likely answer to this crossword clue is the 7 letter word FITNESS
I've seen this crossword clue in The Daily Telegraph
F
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T
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More clues leading to the result FITNESS
Buddy explains!

The straight part
We know that "good health" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case good health = fitness.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 FITNESS mean?
FITNESS noun- The condition of being fit, suitable or appropriate.
- The cultivation of an attractive and/or healthy physique.
- An organism's or species' degree of success in finding a mate and producing offspring.
- The condition of being attractive, fanciable or beautiful.