Setter's at mike using speech for evil purposes (9)
I believe the answer is:
immorally
'for evil purposes' is the definition.
I can't tell whether this definition defines the answer.
'setter's at mike using speech' is the wordplay.
'setter' becomes 'I' (the person who set this crossword).
'at' is a charade indicator (letters next to each other).
'mike' becomes 'M' (phonetic alphabet: alpha, bravo, charlie etc.).
'using speech' becomes 'morally' (I can't justify this - if you can you should give a lot more credence to this answer).
'i'+'m'+'morally'='IMMORALLY'
Can you help me to learn more?
(Another definition for immorally that I've seen is " In a bad way".)