Spirit of Michael Faraday (3)
I believe the answer is:
'spirit' is the definition.
(magical creature)
'of michael faraday' is the wordplay.
'of' says the answer is hidden in the clue.
'ELF' is hidden within 'michael faraday'.
(Other definitions for elf that I've seen before include "Magical being" , "spirit" , "Mischievous youngster" , "Folk tale creature" , "Mischief-maker" .)