Battle stations at first beside border area after retreat (9)
I believe the answer is:
sedgemoor
'battle' is the definition.
(I've seen this before)
'stations at first beside border area after retreat' is the wordplay.
I cannot quite see how this works, but
'border' could be 'edge' (synonyms) and 'edge' is found in the answer.
'area' could be 'moor' (I have seen 'Desolate area ' mean 'moor' so perhaps 'area' could also mean 'moor') and 'moor' is present in the answer.
A single letter 's' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for sedgemoor that I've seen before include "Battle site in Somerset" , "scene of battle" , "Sixteen eighty five battle ending Monmouth's rebellion" .)