A high speed piece of film (4)
I believe the answer is:
clip
This clue might be a double definition.
'a high speed' is the first definition.
'clip' can be an answer for 'speed' (clip can mean something's speed). I'm not certain of the 'a high' bit.
'piece of film' is the second definition.
(I've seen this in another clue)
Can you help me to learn more?
(Other definitions for clip that I've seen before include "Fastener - part of film" , "Cartridge container and piece of film" , "Cut short; cartridge holder" , "sort of joint" , "Extract; cartridge" .)