Begin shooting film's introduction in remake of pioneer (4,4)
I believe the answer is:
open fire
'begin shooting' is the definition.
(I've seen this before)
'film's introduction in remake of pioneer' is the wordplay.
'introduction' indicates taking the first letters.
'in' means one lot of letters goes inside another.
'remake of' is an anagram indicator.
The first letter of 'films' is 'f'.
'pioneer' with letters rearranged gives 'openire'.
'f' put inside 'openire' is 'OPEN-FIRE'.
(Other definitions for open fire that I've seen before include "Traditional room heater" , "Source of heat" , "Begin shooting" , "Get rounds in" , "Perhaps start sniping" .)