Quarrel involving a king's list of duties... (6)
I believe the answer is:
tariff
'list of duties' is the definition.
'quarrel involving a king's' is the wordplay.
'quarrel' becomes 'tiff' (tiff is a kind of quarrel).
'involving' is an insertion indicator.
'a king' becomes 'ar' (I've seen this in other clues**).
'tiff' enclosing 'ar' is 'TARIFF'.
(Other definitions for tariff that I've seen before include "List of customs duties" , "Bill of fare" , "Customs-duty" , "Customs duty" , "Import/export tax" .)