Reveal nothing in policy statement (9)
I believe the answer is:
manifesto
'policy statement' is the definition.
(statement of political policies)
'reveal nothing' is the wordplay.
'reveal' becomes 'manifest' (I've seen this before).
'nothing' becomes 'O' (O resembles 0).
'manifest'+'o'='MANIFESTO'
'in' acts as a link.
(Other definitions for manifesto that I've seen before include "Planks assembled here" , "Publication containing political programme" , "set of political proposals" , "Declaration of intentions by a political party" , "Written declaration of opinions" .)