Layers (4)
'layers' is the definition.
(I know this)
This is all the clue.
(Other definitions for tiers that I've seen before include "I rest in layers" , "Layers, strata" , "More than one bank" , "Rows; levels" , "Tries (anag.)" .)
'layers' is the definition.
(stratum is a kind of layer)
This is the entire clue.
(Other definitions for strata that I've seen before include "Beds of sedimentary rock" , "bands" , "Layers as of rock in the earth's crust" , "Layers of rock on earth's surface" , "Parallel layers" .)
'layers' is the definition.
(hens lay eggs)
This is all the clue.
(Other definitions for hens that I've seen before include "Female chickens" , "Female birds" , "Poultry" , "Birds kept for laying" , "Adult chickens" .)