Wicked American rising: not dead (5)
I believe the answer is:
alive
'not dead' is the definition.
('alive' is the opposite to 'dead')
'wicked american rising' is the wordplay.
'wicked' becomes 'evil' (synonyms).
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'rising' is a reversal indicator (letters written upwards in a down clue).
'evil'+'a'='evila'
'evila' reversed gives 'ALIVE'.
(Other definitions for alive that I've seen before include "Existing - vigorous" , "Still with us" , "Animated and kicking" , "Breathing, existing" , "Spirited" .)