A non-believer’s caught out cleanly (7)
I believe the answer is:
aseptic
'cleanly' is the definition.
Both the answer and definition are adjectives. Perhaps they are linked in a way I don't understand?
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for aseptic that I've seen before include "Free from bacteria, surically clean" , "avoiding germs" , "Sterile" , "Free of bacterial or viral contamination" , "Paciest (anag.)" .)