He sees a hundred new dairy products (7)
I believe the answer is:
cheeses
'dairy products' is the definition.
(cheese is a kind of dairy product)
'he sees a hundred new' is the wordplay.
'a hundred' becomes 'c' (Roman numeral).
'new' indicates anagramming the letters.
'he'+'sees'+'c'='heseesc'
'heseesc' with letters rearranged gives 'CHEESES'.
(Other definitions for cheeses that I've seen before include "'Gruyere, Brie etc. (7)'" , "Camembert, chedder etc." , "Dairy products, can be hard or soft" , "Foods prepared from the pressed curd of milk" , "Stilton and cheddar, perhaps" .)