Court official's argument about criminal past (8)
I believe the answer is:
tipstaff
'court official's' is the definition.
(I've seen this before)
'argument about criminal past' is the wordplay.
'argument' becomes 'tiff' (I've seen this before).
'about' means one lot of letters goes inside another.
'criminal' is an anagram indicator.
'past' with letters rearranged gives 'psta'.
'tiff' enclosing 'psta' is 'TIPSTAFF'.
(Other definitions for tipstaff that I've seen before include "Judge's personal assistant in court" , "Court official" , "One authorised" , "Pat's tiff with the judge" , "Bailiff" .)