Song about endless territory in battleground state (7)
I believe the answer is:
arizona
'state' is the definition.
(Arizona is a US state)
'song about endless territory in battleground' is the wordplay.
I cannot really understand how this works, but
'about' could be 'on' (as in a book 'on' a certain topic) and 'on' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for arizona that I've seen before include "American state with Grand Canyon" , "State of SW USA" , "Dry US state" , "State in south-west US" , "State represented by Senators Barry Goldwater and John McCain" .)