Somewhat selfish little creature
I believe the answer is:
elf
'little creature' is the definition.
(I've seen this in another clue)
'somewhat selfish' is the wordplay.
'somewhat' says the answer is hidden in the clue.
'ELF' is hidden in the letters of 'selfish'.
(Other definitions for elf that I've seen before include "Mischievous sprite" , "A leprechaun" , "Woodland sprite" , "Small supernatural being" , "Naughty child" .)