State Republican keen to suppress independent legislative body (10)
I believe the answer is:
parliament
'legislative body' is the definition.
(a parliament passes legislation)
'state republican keen to suppress independent' is the wordplay.
'state republican' becomes 'par' (I can't justify this - if you can you should believe this answer much more).
'keen' becomes 'lament' (keen can mean to wail with grief).
'to suppress' means one lot of letters goes inside another.
'independent' becomes 'i'.
'lament' enclosing 'i' is 'liament'.
'par'+'liament'='PARLIAMENT'
(Other definitions for parliament that I've seen before include "Houses" , "UK legislature" , "Diet" , "The law is laid down here" , "Legislative assembly" .)