Opening extracted from report Nixon backed (5)
I believe the answer is:
intro
'opening' is the definition.
(short for introduction)
'extracted from report nixon backed' is the wordplay.
'extracted from' indicates the answer is hidden within the clue.
'backed' is a reversal indicator.
'ortni' is hidden within 'report nixon'.
'ortni' backwards is 'INTRO'.
(Other definitions for intro that I've seen before include "Early music piece" , "Preamble" , "Opening bars of a song" , "First bars of a piece of popular music" , "Song's first few bars" .)