Salesperson returning city gentleman's payback (8)
I believe the answer is:
reprisal
'payback' is the definition.
'salesperson returning city gentleman's' is the wordplay.
'salesperson' becomes 'rep' (I've seen this before).
'returning' shows that the letters should be reversed in order.
'city' becomes 'la' (Los Angeles).
'gentleman' becomes 'sir' (I've seen this before).
'la'+'sir'='lasir'
'lasir' backwards is 'risal'.
'rep'+'risal'='REPRISAL'
(Other definitions for reprisal that I've seen before include "Retaliatory deed" , "Retaliation for an injury" , "revenge attack" , "hitting back" , "Counterattack" .)