Artist up in Lovers' Row charges (6)
I believe the answer is:
tariff
'charges' is the definition.
(a tariff is a system of charges)
'artist up in lovers' row' is the wordplay.
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'in' is an insertion indicator.
'lovers' row' becomes 'tiff' (I've seen this before).
'ra' reversed gives 'ar'.
'ar' going inside 'tiff' is 'TARIFF'.
(Other definitions for tariff that I've seen before include "Duty charge" , "Customs duty" , "Export/import duty" , "Tax or duty on a class of imports" , "Import or export duty" .)