Strange European initially somehow becoming an army officer (8)
I believe the answer is:
sergeant
'an army officer' is the definition.
(sergeant is a military rank)
'strange european initially somehow' is the wordplay.
'european' becomes 'E' (abbreviation e.g. EU).
'initially' means one lot of letters go next to another.
'somehow' indicates an anagram.
'strange' put after 'e' is 'estrange'.
'estrange' with letters rearranged gives 'SERGEANT'.
'becoming' is the link.
(Other definitions for sergeant that I've seen before include "NCO or police officer ..." , "military man" , "Police rank" , "Noncommissioned military officer" , "Military rank" .)