Be shown up as wicked (4)
I believe the answer is:
evil
'wicked' is the definition.
('evil' is associated in meaning with 'wicked')
'be shown up' is the wordplay.
'be' becomes 'live' (living is a kind of being).
'shown up' says the letters should be written backwards.
'live' reversed gives 'EVIL'.
'as' is the link.
(Other definitions for evil that I've seen before include "Live badly for badness" , "Great wickedness" , "Morally bad" , "Depraved" , "Wicked or immoral" .)