Those who don't believe in ex-Cuban leader and head of state (8)
I believe the answer is:
infidels
'those who don't believe' is the definition.
The definition suggests an adverb but the answer is not.
'in ex-cuban leader and head of state' is the wordplay.
'ex cuban leader' becomes 'fidel' (I can't explain this - if you can you should believe this answer much more).
'and' is a charade indicator (letters next to each other).
'head of' suggests taking the first letters.
The first letter of 'state' is 's'.
'in'+'fidel'+'s'='INFIDELS'
Can you help me to learn more?
(Another definition for infidels that I've seen is " those who don't act in good faith?".)