Recording verb one dictionary rejected (5)
I believe the answer is:
video
'recording' is the definition.
(I know that video is a type of recording)
'verb one dictionary rejected' is the wordplay.
'verb' becomes 'v' (abbreviation used in dictionaries).
'one' becomes 'i' (Roman numeral).
'dictionary' becomes 'OED' (Oxford English Dictionary).
'rejected' says the letters should be written in reverse.
'oed' backwards is 'deo'.
'v'+'i'+'deo'='VIDEO'
(Other definitions for video that I've seen before include "Recording medium" , "Visible part of a recording" , "Capture on film" , "(Tape for) recorder of film etc" , "TV cassette" .)