How Gladys makes good second film (3,4,8)

I believe the answer is:

the lady vanishes

'film' is the definition.
(I've seen this before)

I don't understand how the rest of the clue works.

(Other definitions for the lady vanishes that I've seen before include "woman goes missing" , "Old film" , "Once prepared for screening" , "Hitchcock film" .)

I've seen this clue in The Times.

Want a hint initially instead of a full solution? Install my app