Military leader is bitter with one US state (8)
I believe the answer is:
missouri
'us state' is the definition.
(I've seen this before)
'military leader is bitter with one' is the wordplay.
'leader' indicates taking the first letters.
'bitter' becomes 'sour' (I've seen this in another clue).
'with' means one lot of letters go next to another.
'one' becomes 'i' (Roman numeral).
The first letter of 'military' is 'm'.
'm'+'is'+'sour'+'i'='MISSOURI'
(Other definitions for missouri that I've seen before include "American state's" , "State south of Iowa" , "State of central US" , "Biggest tributary of the Mississippi" , "Flower" .)