Crossword Genius

A lesson is unethical (6)

Ross

I believe the answer is:

amoral

'unethical' is the definition.
(I've seen this before)

'a lesson' is the wordplay.
'lesson' becomes 'moral' (as in the moral of the story).
'a'+'moral'='AMORAL'

'is' acts as a link.

(Other definitions for amoral that I've seen before include "Having no standards of right or wrong" , "Unconcerned with correctness" , "unconcerned about ethics" , "Unprincipled" , "outrageous!" .)

I've seen this clue in The Mirror.
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