Health is fine, see, after wife left (7)

I believe the answer is:

fitness

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'health' is the definition.
(I've seen this before)

I can't explain the rest of the clue.

(Other definitions for fitness that I've seen before include "condition" , "Well-being" , "Competence" , "Suitability - health" , "State of good health" .)

I've seen this clue in The Sunday Times.

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