Pitch, perhaps, supporting movement (9)
I believe the answer is:
promotion
'pitch perhaps' is the definition.
(pitch is a kind of promotion)
'supporting movement' is the wordplay.
'supporting' becomes 'pro' (I've seen this in other clues).
'movement' becomes 'motion' ('motion' can be a synonym of 'movement'**).
'pro'+'motion'='PROMOTION'
(Other definitions for promotion that I've seen before include "Advancement" , "Puffing, perhaps" , "upgrading" , "Step up" , "sales campaign" .)