Mischievous and somewhat self-involved (5)
I believe the answer is:
elfin
'mischievous' is the definition.
(elfin means like an elf)
'somewhat self-involved' is the wordplay.
'somewhat' indicates a hidden word.
'ELFIN' is hidden in the letters of 'self involved'.
'and' acts as a link.
(Other definitions for elfin that I've seen before include "puckish" , "Small, delicate, mischievous and attractive" , "Resembling one of the little people" , "little character" , "Like a mischievous fairy" .)