Wicked bats flew round (9)
I believe the answer is:
wonderful
'wicked' is the definition.
(I know that wicked can be written as wonderful)
'bats flew round' is the wordplay.
'bats' indicates an anagram (slang for mad).
'flew'+'round'='flewround'
'flewround' with letters rearranged gives 'WONDERFUL'.
(Other definitions for wonderful that I've seen before include "Awe-inspiring" , "Remarkably good" , "Extraordinary" , "Marvellous" , "Excellent" .)