Republican in silly plan (5)
I believe the answer is:
draft
'plan' is the definition.
(I know that draft is a more specific form of the action plan)
'republican in silly' is the wordplay.
'republican' becomes 'r' (abbreviation).
'in' indicates putting letters inside.
'silly' becomes 'daft' (I've seen this in another clue).
'r' put inside 'daft' is 'DRAFT'.
(Other definitions for draft that I've seen before include "Preliminary version or sketch" , "Preliminary outline" , "Rough version" , "Rough sketch" , "Early version of text" .)