Smart trick (5)
I believe the answer is:
sting
I believe this is a double definition.
'smart' is the first definition.
(both can mean to burn or hurt)
'trick' is the second definition.
(sting can mean a cheat or trick)
(Other definitions for sting that I've seen before include "Con: leader singer of Police" , "Entrapment operation; sharp pain" , "The pain caused by bee or nettle" , "Wound from wasp" , "Sharp tingling pain" .)