Crispy cookie (5)
I believe the answer is:
wafer
'crispy cookie' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for wafer that I've seen before include "Thin, crisp biscuit or bread" , "A very thin plain biscuit" , "Ice cream biscuit" , "Very thin slice" , "Thin type" .)