Ferret out to catch a plague (5)
I believe the answer is:
haunt
'plague' is the definition.
(thesaurus)
'ferret out to catch a' is the wordplay.
I cannot quite understand how this works, but
'a' is present in the answer.
'catch' could be 'hunt' (hunting is a kind of catching) and 'hunt' is found in the remaining letters.
This accounts for all the letters.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for haunt that I've seen before include "Frequent (a place)" , "A favourite place" , "Frequent - resort" , "Mainfest presence as ghost does" , "Visit as a ghost" .)