Spoil opening of film after error (2,3)
I believe the answer is:
go off
'spoil' is the definition.
(thesaurus)
'opening of film after error' is the wordplay.
'opening of' suggests taking the first letters.
'after' says to put letters next to each other.
'error' becomes 'goof' (I've seen this in another clue).
The initial letter of 'film' is 'f'.
'f' put after 'goof' is 'GO-OFF'.
(Other definitions for go off that I've seen before include "Explode" , "Fire" , "Decay - become disenchanted with" , "fall asleep" , "Turn" .)