Greek character, inspiring talker shut up (5)
I believe the answer is:
muted
'shut up' is the definition.
Both the definition and answer are adjectives. Perhaps they are linked in a way I don't understand?
'greek character inspiring talker' is the wordplay.
'greek character' becomes 'mu' (letter from the Greek alphabet).
'inspiring talker' becomes 'ted' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'mu'+'ted'='MUTED'
Can you help me to learn more?
(Other definitions for muted that I've seen before include "with reduced volume" , "Viola is sometimes" , "Temporarily speechless" , "(Of sound/colour) softened" , "Kept quiet" .)