British haul in each caviar supplier (6)
I believe the answer is:
beluga
'caviar supplier' is the definition.
'british haul in each' is the wordplay.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'haul' becomes 'lug' (I've seen this before).
'in' means one lot of letters goes inside another.
'each' becomes 'ea'.
'lug' placed into 'ea' is 'eluga'.
'b'+'eluga'='BELUGA'
(Other definitions for beluga that I've seen before include "Could a bugle be a source of caviar?" , "Small white whale; type of caviar" , "Species of sturgeon" , "large marine creature" , "Great Russian sturgeon - Arctic whale" .)