American officer showing the flag (6)
I believe the answer is:
ensign
This clue is a double definition.
'american officer' is the first definition.
(I've seen this before)
'the flag' is the second definition.
('ensign' can be a synonym of 'flag')
'showing' acts as a link.
(Other definitions for ensign that I've seen before include "Flying" , "Flag; rank" , "National flag" , "Flag; standard-bearer" , "Ship's flag and junior officer" .)