Figure given by Defense Department (8)
I believe the answer is:
pentagon
I believe this clue is a double definition.
'figure' is the first definition.
(type of geometrical figure)
'defense department' is the second definition.
(the Pentagon is the US Department of Defense)
'given by' acts as a link.
(Other definitions for pentagon that I've seen before include "government HQ abroad" , "A shape; Arlington HQ" , "rectangle snipped at one corner?" , "military leadership" , "US military leaders" .)