The most common and most likely answer to this crossword clue is the 4 plus 6 letter word ABLE BODIED
I've seen this crossword clue in Financial Times
A
B
L
E
B
O
D
I
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D
More clues leading to the result ABLE BODIED
Buddy explains!

The straight part
We know that "fit and healthy" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fit and healthy = able bodied.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 ABLE BODIED mean?
ABLE BODIED adjective- Having a sound, strong body; physically competent; robust; fit for service.
- Capable of performing all requisite duties as a seaman, specifically in the Royal Navy, a rating between leading and ordinary.