Case of Greek wine sent back by foremost of customers (8)
I believe the answer is:
canister
'case' is the definition.
(thesaurus)
'greek wine sent back by foremost of customers' is the wordplay.
'greek wine' becomes 'retsina' (I've seen this before).
'sent back' is a reversal indicator.
'by' says to put letters next to each other.
'foremost of' says to take the initial letters.
The first letter of 'customers' is 'c'.
'retsina' written backwards gives 'anister'.
'anister' put after 'c' is 'CANISTER'.
'of' is the link.
(Other definitions for canister that I've seen before include "Metal storage container" , "Metal food container" , "Container for a film reel" , "Metal case" , "Vessel" .)