Film actor wanting lead in Psycho (5)
I believe the answer is:
layer
'film' is the definition.
(film can mean a thin layer of something)
I cannot understand how the rest of the clue works.
(Other definitions for layer that I've seen before include "Single thickness and hen" , "Stratum; eg, hen" , "Seam" , "Thin sheet - productive hen" , "Coating" .)