A better type of cake (5)
I believe the answer is:
layer
'type of cake' is the definition.
(I've seen this in another clue)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for layer that I've seen before include "Coating" , "Source of eggs" , "Single thickness, tier" , "One supplying eggs" , "Stratum, tier" .)