Employing a piece of dubious ingenuity (5)
I believe the answer is:
using
'employing' is the definition.
(to employ is to use)
'a piece of dubious ingenuity' is the wordplay.
'a piece of' indicates the answer is hidden within the clue.
'USING' is hidden within 'dubious ingenuity'.
(Other definitions for using that I've seen before include "having recourse to" , "Putting into service" , "Employing" , "taking drugs" , "Exercising" .)