Unethical; sinful (7)
I believe the answer is:
immoral
This clue is a double definition.
'unethical' is the first definition.
(synonyms)
'sinful' is the second definition.
(I've seen this before)
(Other definitions for immoral that I've seen before include "sick" , "Ignoring right and wrong" , "Without values" , "Dissolute or unprincipled" , "Unethical, unprincipled" .)