A thankless wretch (7)
I believe the answer is:
ingrate
'a thankless wretch' is the definition.
(synonyms)
This is all the clue.
(Other definitions for ingrate that I've seen before include "He doesn't appreciate" , "one offers no thanks" , "Unappreciative character" , "Thankless person from Tangier" , "One unappreciative" .)