Obliged to great flu treatment (8)
I believe the answer is:
grateful
'obliged' is the definition.
(I've seen this in another clue)
'great flu treatment' is the wordplay.
'treatment' is an anagram indicator (letters treated or processed differently).
'great'+'flu'='greatflu'
'greatflu' is an anagram of 'GRATEFUL'.
'to' is the link.
(Other definitions for grateful that I've seen before include "quantity of coal" , "Felt a rug (anag)" , "Showing thankfulness" , "Showing gratitude" , "Showing appreciation for kindness" .)