Very fine biscuit with no excess fat (5-4)
I believe the answer is:
Here is my best explanation:
'very fine' is the definition.
(I've seen this before)
'biscuit with no excess fat' is the wordplay.
'biscuit' becomes 'wafer' (wafer is a kind of biscuit).
'with no excess fat' becomes 'thin' (I can't justify this - if you can you should believe this answer much more).