Additional actor (5)
I believe the answer is:
extra
I believe this is a double definition.
'additional' is the first definition.
(extra means additional or surplus)
'actor' is the second definition.
(extra is a type of actor)
(Other definitions for extra that I've seen before include "Additional expense" , "One has no lines" , "Additional, like non-speaking actor" , "Bit player in film" , "on top" .)