Charge a Republican involved in dispute (6)
I believe the answer is:
tariff
'charge' is the definition.
(tariff is a kind of charge)
'a republican involved in dispute' is the wordplay.
'republican' becomes 'r' (abbreviation).
'involved in' means one lot of letters goes inside another.
'dispute' becomes 'tiff' (tiff is a kind of dispute).
'a'+'r'='ar'
'ar' placed into 'tiff' is 'TARIFF'.
(Other definitions for tariff that I've seen before include "Import/export tax" , "Fees schedule" , "List of fixed charges as in hotel" , "Table of fixed charges" , "Table of (hotel) charges" .)