Fiendish new setter caught on tape? (7)
I believe the answer is:
demonic
'fiendish' is the definition.
(synonyms)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for demonic that I've seen before include "Inspired as if by a fiend" , "Like evil spirits" , "Fiendish or satanic" , "Furious" , "Devilish" .)