Cast-of-thousands film (4)
I believe the answer is:
epic
'cast-of-thousands film' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for epic that I've seen before include "On a grand scale like long poem" , "Long adventure story" , "Larger than life" , "Of heroic proportions" , "Long poem telling of heroic events" .)