I believe the answer is:
'impish sort' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for rascal that I've seen before include "Mischievous or cheeky child" , "mischief-maker" , "Rogue or cheeky child" , "Mischievous person or confused lascar" , "Michievous person/child" .)