Anti-aircraft fire moving left, one coming in twice secures disputed territory (8,7)
I believe the answer is:
falkland islands
'disputed territory' is the definition.
(I know that Falkland Islands is a disputed territory)
'anti-aircraft fire moving left one coming in twice secures' is the wordplay.
I cannot really understand how this works, but
'left' could be 'al' (I've seen this in other clues) and 'al' is located in the answer.
'one' could be 'an' (an apple is one apple) and 'an' is found within the answer.
'secures' could be 'lands' (land can mean to obtain or secure) and 'lands' is found in the answer.
This explanation may well be incorrect...
(Another definition for falkland islands that I've seen is " British possession in the South Atlantic".)