Layers of desserts from the east — Arabia primarily (6)
I believe the answer is:
strata
'layers' is the definition.
(I know this)
'desserts from the east arabia primarily' is the wordplay.
'desserts' becomes 'tarts' (I've seen this in another clue).
'from the east' says the letters should be written in reverse (on a map from right to left).
'primarily' indicates taking the first letters.
The initial letter of 'arabia' is 'a'.
'tarts' reversed gives 'strat'.
'strat'+'a'='STRATA'
'of' is the link.
(Other definitions for strata that I've seen before include "Layers as of rocks in earth's crust" , "Levels, grades or social classes" , "Parallel layers" , "Layers into which rocks are divided" , "Layers of sedimentary rock" .)