Film of hen? (5)
I believe the answer is:
layer
This clue is a double definition.
'film' is the first definition.
(film can mean a thin layer of something)
'hen?' is the second definition.
(something which lays - eggs in this case)
'of' is the link.
(Other definitions for layer that I've seen before include "Bed - hen" , "Stratum; chicken" , "One who does the setting" , "plate?" , "Single thickness and hen" .)