Outsmart (6)
I believe the answer is:
outwit
'outsmart' is the definition.
(I know that outsmart can be written as outwit)
This is the entire clue.
(Other definitions for outwit that I've seen before include "Mentally get the better of" , "Outsmart" , "Defeat by superior ingenuity" , "Outfox" , "Intellectually get the better of" .)