Terribly posh for a consumer (7)
I believe the answer is:
shopper
'consumer' is the definition.
(shopper is a kind of consumer)
'terribly posh for a' is the wordplay.
'terribly' indicates anagramming the letters.
'for' says to put letters next to each other.
'a' becomes 'per'.
'posh' with letters rearranged gives 'shop'.
'shop'+'per'='SHOPPER'
(Other definitions for shopper that I've seen before include "basket" , "selling?" , "One making purchases" , "Large bag" , "Customer" .)