Edging away, other troops leading at that point (9)
I believe the answer is:
thereupon
'at that point' is the definition.
(I've seen this before)
'edging away other troops leading' is the wordplay.
'edging away' means to look at the middle letters.
'troops' becomes 're' (I've seen this in other clues).
'leading' becomes 'upon' (**).
The centre of 'other' is 'the'.
'the'+'re'+'upon'='THEREUPON'
(Other definitions for thereupon that I've seen before include "Shortly after that" , "straight afterwards" , "straightaway" , "at that point" , "immediately after that" .)