No square dealings in this seat of power? (4,6)
I believe the answer is:
oval office
'this seat of power?' is the definition.
(the Oval Office is the office of the US president)
'no square dealings' is the wordplay.
'no square' becomes 'oval'.
'dealings' becomes 'office' (I can't justify this - if you can you should believe this answer much more).
'oval'+'office'='OVAL OFFICE'
'in' is the link.
(Other definitions for oval office that I've seen before include "US president's workplace" , "room for president" , "Where US presidents have their desk" , "US presidential room" .)