One's state of health and suitability (7)
I believe the answer is:
fitness
This clue is a triple definition!
'one's state' is the first definition.
'fitness' can be an answer for 'state' (fitness is a kind of state). I am not certain of the 'one's' bit.
'of' acts as a link.
'health' is the second definition.
(I've seen this before)
'and' acts as a link.
'suitability' is the third definition.
(fitness is a kind of suitability)
Can you help me to learn more?
(Other definitions for fitness that I've seen before include "State of good health" , "condition" , "Well-being" , "Competence" , "Suitability - health" .)