Clue: Edmund C Bentley, for instance mocked gently; Vivaldi, when cut, cut again (8)
Answer: CLERIHEW
Explanation: Definition: Edmund C Bentley, for instance mocked gently
Edmund CLERIHEW Bentley gave his name to a form of humorous biographical poem 
 Vivaldi was a CLERI[c] with the last letter "cut"; plus HEW="cut" again
 *Edit – see Muffyword @8 – the clue is itself a clerihew poem