Disgrace made me a nonentity in some parts (6)
I believe the answer is:
demean
'disgrace' is the definition.
(I know that disgrace can be written as demean)
'made me a nonentity in some parts' is the wordplay.
'some parts' says the answer is hidden in the clue (part of the clue provides the answer).
'DEMEAN' can be found hidden inside 'made me a nonentity in'.
(Other definitions for demean that I've seen before include "Cause (someone) to lose dignity" , "Lower in dignity or reputation" , "'Put down, degrade (6)'" , "Discredit" , "Lower in reputation, shame" .)