The most common and most likely answer to this crossword clue is the 9 letter word HEALTHIER
H
E
A
L
T
H
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R
More clues leading to the result HEALTHIER
- More wholesome cure by Doctor Reith
- Try to keep lithe, training to be so?
- The man needing to change — hospital one enters, becoming this?
- Before trial he bungled, that man could be in better shape
- She has a lithe body, is fitter
- Better rendition of “Hi there, Al”
- Fitter needs wherewithal when struggling to remove both weights
- Husband richer after leaving wife in a better position financially
- Learn about officer with hurry to get fitter
Buddy explains!

The straight part
We know that "Fitter" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fitter = healthier.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 HEALTHIER mean?
HEALTHIER adjective- Enjoying health and vigor of body, mind, or spirit: well.
- Conducive to health.
- Evincing health.
- Significant, hefty; beneficial.