Maria with us battling warrior (7)
I believe the answer is:
samurai
'warrior' is the definition.
(I know that samurai is a type of warrior)
'maria with us battling' is the wordplay.
'with' means one lot of letters go next to another.
'battling' indicates anagramming the letters (I've seen 'battle' mean this (the letters disrupted as if in battle)).
'maria' put after 'us' is 'usmaria'.
'usmaria' anagrammed gives 'SAMURAI'.
(Other definitions for samurai that I've seen before include "military man" , "Japanese militarist" , "Sudoku variant" , "Member of Japanese warrior caste" , "Japanese warrior code" .)