President's national barrier (5)
I believe the answer is:
chair
This could be a double definition.
'president's' is the first definition.
(synonyms)
'national barrier' is the second definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe they are linked in a way I don't understand?
Can you help me to learn more?
(Other definitions for chair that I've seen before include "Preside over - seat" , "Presiding officer" , "control meeting" , "Movable seat" , "What professor has" .)