Purported cure tested her good faith (4,2,3,3)
I believe the answer is:
hair of the dog
'purported cure' is the definition.
(supposed cure for a hangover)
'tested her good faith' is the wordplay.
'tested' is an anagram indicator (letters tested or stressed into a new form).
'her'+'good'+'faith'='hergoodfaith'
'hergoodfaith' anagrammed gives 'HAIR OF THE DOG'.
(Other definitions for hair of the dog that I've seen before include "breakfast-time drink?" , "Treatment for bad head" , "Alcohol taken to "cure" a hangover" , "Morning tipple after night of excessive drinking" , "'...that bit one' completes a dubious hangover remedy" .)