Support reduction in setting (8)
I believe the answer is:
backdrop
'setting' is the definition.
(I've seen this before)
'support reduction' is the wordplay.
'support' becomes 'back' (to back is to support or endorse).
'reduction' becomes 'drop' (I've seen this in another clue).
'back'+'drop'='BACKDROP'
'in' acts as a link.
(Other definitions for backdrop that I've seen before include "Painted rear stage cloth" , "Setting for a scene" , "Against which action is played out" , "Wider view" , "Scenery hung at the rear of a stage" .)