Back soldiers with the wild distinctive mark (9)
I believe the answer is:
signature
'distinctive mark' is the definition.
(I've seen this before)
'back soldiers with the wild' is the wordplay.
'back' is a reversal indicator.
'soldiers' becomes 'gis' (I've seen this in other clues**).
'with' is a charade indicator (letters next to each other).
'the wild' becomes 'nature' ('nature' can be a synonym of 'wild').
'gis' written backwards gives 'sig'.
'sig'+'nature'='SIGNATURE'
(Other definitions for signature that I've seen before include "Distinctive mark" , "Name written by its owner" , "Personal mark" , "ending to letter?" , "distinctive style" .)