Fine tonic cured disease (9)
I believe the answer is:
infection
'disease' is the definition.
(infection is a kind of health problem)
'fine tonic cured' is the wordplay.
'cured' is an anagram indicator.
'fine'+'tonic'='finetonic'
'finetonic' with letters rearranged gives 'INFECTION'.
(Other definitions for infection that I've seen before include "what may be caught" , "Disease caught" , "Process of catching virus" , "Invasion by pathogenic micro-organism" , "viral illness" .)