The ultimate customer (3,4)
I believe the answer is:
end user
'the ultimate customer' is the definition.
(someone who ends up using a product)
This is all the clue.
(Other definitions for end user that I've seen before include "Being last to receive goods" , "Final recipient of product" , "Ensured (anag.)" , "One getting the ultimate enjoyment" , "Final consumer" .)