Clara's mischievous scoundrel (6)
I believe the answer is:
rascal
'scoundrel' is the definition.
(rascal is a kind of scoundrel)
'clara's mischievous' is the wordplay.
'mischievous' is an anagram indicator.
'claras' anagrammed gives 'RASCAL'.
(Other definitions for rascal that I've seen before include "Rogue or cheeky child" , "'Scoundrel, rogue (6)'" , "Scoundrel or mischievous child" , "Pickle" , "A mischievous and maybe dishonest person" .)