Cake tier (5)
I believe the answer is:
layer
'cake tier' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for layer that I've seen before include "Blanket - single thickness" , "Stratum; eg, hen" , "Single thickness, tier" , "Stratum; chicken" , "Tier or thickness - or a hen?" .)