Pace in American territory (6)
I believe the answer is:
canter
'pace' is the definition.
(I know that canter is a kind of pace)
'in american territory' is the wordplay.
'in' indicates the answer is hidden within the clue.
'CANTER' can be found hidden inside 'american territory'.
(Other definitions for canter that I've seen before include "Moderate pace for horse" , "Run" , "Ride at a quick pace" , "(Horse's) pace between a trot and a gallop" , "Horse gait quicker than 9 across" .)