Victor against odd disheartened soldiers (9)
I believe the answer is:
conqueror
'victor' is the definition.
(I know that conqueror is a type of victor)
'against odd disheartened soldiers' is the wordplay.
'against' becomes 'con' (as in pros and cons, for and against).
'odd' becomes 'queer' (I've seen this in another clue).
'disheartened' means to remove the middle letters.
'soldiers' becomes 'OR' (Other Ranks).
'queer' with its middle removed is 'quer'.
'con'+'quer'+'or'='CONQUEROR'
(Other definitions for conqueror that I've seen before include "Military victor" , "William's title after 1066 battle" , "William of Normandy" , "For one, William" , "humbler?" .)