Endearingly mischievous sort (6)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
rascal
(Other definitions for rascal that I've seen before include "Lascar (anag.)" , "Horror" , "Mischievous person or confused lascar" , "Scoundrel or mischievous child" , "Mischievous or cheeky person" .)