Crowd actors (6)
I believe the answer is:
extras
'crowd actors' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for extras that I've seen before include "People employed in crowd scenes in film" , "Runs not scored from the bat" , "Film actors in small non-speaking roles like crowd scenes" , "Additions" , "Add-ons" .)