National Express (5)
I believe the answer is:
state
This clue is a double definition.
'national' is the first definition.
(thesaurus)
'express' is the second definition.
(I know that express can be written as state)
(Other definitions for state that I've seen before include "Declare - political unit" , "A test (anag.)" , "Say; country" , "Declare; affirm" , "See 3" .)