Magical creature featured in selfie (3)
I believe the answer is:
elf
'magical creature' is the definition.
(creature in fairy tales)
'featured in selfie' is the wordplay.
'featured in' says the answer is hidden in the clue.
'ELF' can be found hidden inside 'selfie'.
(Other definitions for elf that I've seen before include "Imaginary small being of selfish kind" , "Supernatural creature of folk tales" , "tiny little chap" , "A leprechaun" , "1 ac fairy" .)