Stagger for part of the film (4)
I believe the answer is:
reel
I believe this is a triple definition!
'stagger' is the first definition.
(both can mean to move around without balance)
'for part' is the second definition.
(I have seen 'Part of film' mean 'reel' so perhaps 'part' could also mean 'reel')
'of' acts as a link.
'the film' is the third definition.
(reel is a kind of film)
(Other definitions for reel that I've seen before include "Whirl around" , "Drum - dance - music" , "Lively dance or fishing rod controller" , "Part of a film; stagger" , "wind-up?" .)