Charlie on border in film sample (4)
I believe the answer is:
clip
'film sample' is the definition.
(I've seen this in another clue)
'charlie on border' is the wordplay.
'charlie' becomes 'c' (phonetic alphabet: alpha, bravo, charlie etc.).
'on' says to put letters next to each other.
'border' becomes 'lip' (I've seen this in another clue).
'c'+'lip'='CLIP'
'in' acts as a link.
(Other definitions for clip that I've seen before include "Fastener; cut short" , "Trim; film extract" , "Device for holding papers together" , "Shorten" , "Fastener; trim" .)