No part exchange for this customer (6)
I believe the answer is:
patron
'this customer' is the definition.
(I've seen this before)
'no part exchange' is the wordplay.
'exchange' is an anagram indicator.
'no'+'part'='nopart'
'nopart' with letters rearranged gives 'PATRON'.
'for' is the link.
(Other definitions for patron that I've seen before include "Patrick for Ireland, for example" , "Sponsor or supporter as of the arts" , "Regular customer; backer" , "Restaurant customer" , "Saint" .)