To ratify in parliament (4)
I believe the answer is:
amen
'to ratify' is the definition.
(thesaurus)
'in parliament' is the wordplay.
'in' indicates a hidden word.
'AMEN' is hidden within 'parliament'.
(Other definitions for amen that I've seen before include "Response to prayer" , "Put name to end of payer" , "Name for prayer's end" , "statement of affirmation" , "Approve" .)