Small camp some distance away from the main army (7)
I believe the answer is:
outpost
'small camp some distance away from the main army' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for outpost that I've seen before include "isolated settlement" , "Distant military camp" , "Remote part of an empire" , "Remote settlement" , "Distant part (of empire)" .)