Kept in pelf, inclined to be mischievous (5)
I believe the answer is:
elfin
'mischievous' is the definition.
(elfin means like an elf)
'kept in pelf inclined to' is the wordplay.
'kept in' indicates a hidden word.
'ELFIN' is hidden in the letters of 'pelf inclined to'.
'be' acts as a link.
(Other definitions for elfin that I've seen before include "little character" , "Delicate, slight" , "Like a mischievous fairy" , "Petite and charming" , "Small, delicate and charming" .)