Obliterate boils treated in a hospital (7)
I believe the answer is:
abolish
'obliterate' is the definition.
(thesaurus)
'boils treated in a hospital' is the wordplay.
'treated' is an anagram indicator.
'in' indicates putting letters inside.
'hospital' becomes 'h' (abbreviation for hospital on maps).
'boils' anagrammed gives 'bolis'.
'a'+'h'='ah'
'bolis' placed into 'ah' is 'ABOLISH'.
(Other definitions for abolish that I've seen before include "Put an end to, formally" , "Annul - eradicate" , "Put an end to (custom)" , "Axe" , "ditch" .)