A fruity pastry’s inverted layers (6)
I believe the answer is:
strata
'layers' is the definition.
(stratum is a kind of layer)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for strata that I've seen before include "Layers or thicknesses of earth" , "Geological layers" , "Layers as of rock in the earth's crust" , "Parallel layers" , "Beds of sedimentary rock" .)