Arch (7)
I believe the answer is:
roguish
'arch' is the definition.
(thesaurus)
This is the entire clue.
(Other definitions for roguish that I've seen before include "Dishonest - mischievous" , "Playfully mischievous" , "Mischievous; unprincipled" , "I gush or change to be waggish" , "reprobate" .)