Cut width in layer (4)
I believe the answer is:
hewn
'cut' is the definition.
(synonyms)
'width in layer' is the wordplay.
'width' becomes 'w' (abbreviation in geometry).
'in' means one lot of letters goes inside another.
'layer' becomes 'hen' (hens lay eggs).
'w' placed into 'hen' is 'HEWN'.
(Other definitions for hewn that I've seen before include "Cut with an axe or chisel" , "Axed" , "Cut with blows" , "Chopped roughly" , "Shaped as with an axe" .)