Thin crisp biscuit (5)
I believe the answer is:
wafer
'thin crisp biscuit' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for wafer that I've seen before include "Very thin slice" , "Light thin biscuit" , "Communion bread" , "Ice cream biscuit" , "Ice cream's biscuit" .)