Nation securing superior sculpture (6)
I believe the answer is:
statue
'sculpture' is the definition.
(statue is a kind of sculpture)
'nation securing superior' is the wordplay.
'nation' becomes 'state' ('state' can be a synonym of 'nation'**).
'securing' means one lot of letters goes inside another.
'superior' becomes 'u' (I've seen this in other clues).
'state' going around 'u' is 'STATUE'.
(Other definitions for statue that I've seen before include "bust" , "Figurine" , "Solid representation of the human form" , "Carved representation" , "Monument" .)