The chairman's seat? (5)
I believe the answer is:
sedan
'the chairman's seat?' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
This is all the clue.
Can you help me to learn more?
(Other definitions for sedan that I've seen before include "big chair" , "Four-door car" , "Battle in 1940" , "outmoded form of transport" , "Dean's in an old conveyance" .)