Erase nothing in video (4)
I believe the answer is:
void
'erase' is the definition.
(thesaurus)
'nothing in video' is the wordplay.
'nothing' becomes 'O' (looks like zero - 0).
'in' means one lot of letters goes inside another.
'video' becomes 'vid' (short for video).
'o' put within 'vid' is 'VOID'.
(Other definitions for void that I've seen before include "Blank, invalid" , "Empty or vacant, like space" , "Not valid or legally binding" , "Emptiness, empty space" , "absence of a suit" .)