Resignation about blunder, in part (9)
I believe the answer is:
surrender
'resignation' is the definition.
(I know that resignation can be written as surrender)
'about blunder in part' is the wordplay.
'about' shows that the letters should be reversed in order.
'blunder' becomes 'err' (to err is to make a mistake or blunder).
'in' is an insertion indicator.
'part' becomes 'sunder' (I've seen this before).
'err' reversed gives 'rre'.
'rre' placed inside 'sunder' is 'SURRENDER'.
(Other definitions for surrender that I've seen before include "Cede" , "Capitulate, relinquish" , "Wave the white flag" , "Hand over" , "Yield, give in" .)