Reportedly true film (4)
I believe the answer is:
reel
'film' is the definition.
(reel is a kind of film)
'reportedly true' is the wordplay.
'reportedly' indicates a 'sounds like' (homophone) clue.
'true' becomes 'real' ('real' can be similar in meaning to 'true').
'real' sounds like 'REEL'.
(Other definitions for reel that I've seen before include "Move unsteadily (like a Scottish dancer?)" , "spin" , "Lively dance or fishing rod controller" , "Stagger with rod winder" , "Lively Scottish dance" .)