Biscuit ends in hollow area of the floor (5)
I believe the answer is:
wafer
'biscuit' is the definition.
(wafer is a kind of biscuit)
'ends in hollow area of the floor' is the wordplay.
'ends in' says to take the final letters (I've seen 'end in' mean this).
The final letters of 'hollow area of the floor' are 'WAFER'.
(Other definitions for wafer that I've seen before include "Ice-cream biscuit" , "Communion bread" , "A very thin plain biscuit" , "thin stuff" , "Ice cream biscuit" .)