Presidential office shape (4)
I believe the answer is:
oval
'presidential office shape' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for oval that I've seen before include "Egg shape - Kennington test match venue" , "Where a duck may be broken" , "Ellipsoidal" , "Surrey county cricket ground" , "Ellipse" .)