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