Everlasting, timeless, unethical (7)
I believe the answer is:
immoral
'unethical' is the definition.
(synonyms)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for immoral that I've seen before include "Not conforming to accepted rules of conduct, particularly in sexual matters" , "Licentious - dissolute" , "dishonest" , "Evil" , "Without a sense of right and wrong" .)