Complete discretion after Northern Ireland's backtracking (6)
I believe the answer is:
intact
'complete' is the definition.
(intact can mean complete or undamaged)
'discretion after northern ireland's backtracking' is the wordplay.
'discretion' becomes 'tact' (being tactful is being discreet).
'after' is a charade indicator (letters next to each other).
'northern ireland' becomes 'NI' (abbreviation).
'backtracking' says the letters should be written backwards.
'ni' backwards is 'in'.
'tact' after 'in' is 'INTACT'.
(Other definitions for intact that I've seen before include "Entire and whole" , "All in one piece" , "Unscathed" , "Complete - unbroken" , "Entire, undamaged" .)