A hen in bed (5)
I believe the answer is:
layer
I believe this is a double definition.
'a hen' is the first definition.
(something which lays - eggs in this case)
'bed' is the second definition.
(I know that bed can be written as layer)
'in' acts as a link.
(Other definitions for layer that I've seen before include "One of several thicknesses" , "Blanket - single thickness" , "Stratum; chicken" , "One supplying eggs" , "Bed - hen" .)