Caviare? Very thin gourmand has the lot (10)
I believe the answer is:
everything
'the lot' is the definition.
(I've seen this before)
'caviare? very thin gourmand has' is the wordplay.
'has' indicates a hidden word.
'EVERYTHING' is hidden within 'caviare very thin gourmand'.
(Other definitions for everything that I've seen before include "The whole shebang" , "the works" , "great deal" , "All that is; life in general" , "All items" .)