Deceitful, underhand (7)
I believe the answer is:
devious
I believe this clue is a double definition.
'deceitful' is the first definition.
(thesaurus)
'underhand' is the second definition.
(I've seen this before)
(Other definitions for devious that I've seen before include "Not straightforward, underhand" , "Scheming, underhand" , "Underhand -- sneaky" , "Machiavellian, roundabout" , "Going astray" .)