Fool captured enemy territory (7)
I believe the answer is:
airhead
'fool' is the definition.
(I've seen this in another clue)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for airhead that I've seen before include "military base behind enemy lines" , "Dope" , "Someone with nothing between the ears?" , "One not very bright" , "Stupid person" .)