Greek character actor without subtlety, crazy man (8)
I believe the answer is:
muhammad
'man' is the definition.
'greek character actor without subtlety crazy' is the wordplay.
I cannot really understand how this works, but
'character' could be 'mu' (Greek letter) and 'mu' is found in the answer.
'actor' could be 'ham' (ham is a kind of actor) and 'ham' is located in the answer.
'crazy' could be 'mad' (synonyms) and 'mad' is found within the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for muhammad that I've seen is " Founder of the Islamic faith".)