Argument about a right scale of penalties (6)
I believe the answer is:
Here is my best explanation:
'scale of penalties' is the definition.
'argument about a right' is the wordplay.
'argument' becomes 'tiff' (I've seen this before).
'about' indicates putting letters inside.
'a right' becomes 'ar' (I've seen this in other clues).
'tiff' placed around 'ar' is 'TARIFF'.
(Other definitions for tariff that I've seen before include "Table of (hotel) charges", "Sentencing scale", "Menu", "Export/import duty", "Rate", "Tax or duty to be paid on some imports or exports", "Duty charge", "Bill of fare", "Fees schedule" and "Import or export duty".)