Somehow estrange the military man (8)
I believe the answer is:
sergeant
'the military man' is the definition.
(sergeant is a kind of military man)
'somehow estrange' is the wordplay.
'somehow' is an anagram indicator.
'estrange' with letters rearranged gives 'SERGEANT'.
(Other definitions for sergeant that I've seen before include "Army rank" , "Man in charge" , "Military or police officer" , "Rank above corporal" , "Troy" .)