Plan alternative cinema equipment (9)
I believe the answer is:
projector
'cinema equipment' is the definition.
(I've seen this before)
'plan alternative' is the wordplay.
'plan' becomes 'project' (project is a kind of plan).
'alternative' becomes 'or' (**).
'project'+'or'='PROJECTOR'
(Other definitions for projector that I've seen before include "Cinema equipment" , "Slide-showing device" , "Cinema machine" , "Optical instrument that extends an image onto a screen" , "Device for showing slides or film on a screen" .)