Overrides a decision to include controversial nobleman (2,4)
I believe the answer is:
de sade
'controversial nobleman' is the definition.
(Marquis de Sade)
'overrides a decision to include' is the wordplay.
'to include' says the answer is hidden in the clue.
'DE SADE' can be found hidden inside 'overrides a decision'.
(Other definitions for de sade that I've seen before include "Notorious French marquis, d. 1814" , "The Marquis . . . . . . is a byword for cruelty" , "French author many considered depraved" .)