Stand by manifesto (8)
I believe the answer is:
platform
I believe this clue is a double definition.
'stand' is the first definition.
(I've seen this before)
'manifesto' is the second definition.
(I've seen this before)
'by' acts as a link.
(Other definitions for platform that I've seen before include "Raised horizontal surface" , "Part of railway station" , "soapbox" , "Stage; station area" , "Shoe with a high, thick sole" .)