Instrument set up in video booth (4)
I believe the answer is:
oboe
'instrument' is the definition.
(type of musical instrument)
'set up in video booth' is the wordplay.
'set up' says the letters should be written in reverse (in a down clue, letters go up).
'in' indicates the answer is hidden within the clue.
'eobo' is hidden within 'video booth'.
'eobo' in reverse letter order is 'OBOE'.
(Other definitions for oboe that I've seen before include "Woodwind instrument of treble pitch" , "Orchestral piece" , "Musical instrument" , "Source of music" , "blow it!" .)