Draw up and turn gun on US top brass (8)
I believe the answer is:
pentagon
'top brass' is the definition.
(I've seen this before)
'draw up and turn gun on' is the wordplay.
'draw up' becomes 'pen' (I can't explain this - if you can you should give a lot more credence to this answer).
'and' means one lot of letters go next to another.
'turn' is a reversal indicator.
'gun' becomes 'gat' (US informal term for a gun).
'gat' back-to-front is 'tag'.
'pen'+'tag'+'on'='PENTAGON'
'us' is the link.
I am not very happy about this link. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for pentagon that I've seen before include "Headquarters of USA Department of Defence" , "Figure - US military HQ" , "US building of high security" , "US military leaders" , "Five-sided polygon" .)