Minor actors in crowd scenes (6)
I believe the answer is:
extras
'minor actors in crowd scenes' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for extras that I've seen before include "Actors hired for crowd scenes" , "Spear-carriers" , "Bit players, actors without dialogue" , "Minor actors in crowd scenes" , "Sundries" .)