Failed to hear sound of film (6)
I believe the answer is:
missed
'failed' is the definition.
(missing is a kind of failing)
'sound of film' is the wordplay.
'sound of' indicates a 'sounds like' (homophone) clue.
'film' becomes 'mist' (to film over is to mist or fog over).
'mist' sounds like 'MISSED'.
'to hear' acts as a link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for missed that I've seen before include "Failed to hit target" , "Overlooked; needed" , "Avoided" , "Didn't catch" , "failed to see" .)