French veto letting in another European military leader (8)
I believe the answer is:
napoleon
'military leader' is the definition.
(Napoleon Bonaparte was a military leader)
'french veto letting in another european' is the wordplay.
'french veto' becomes 'non' (French for 'no', a word which might veto something).
'letting in' is an insertion indicator.
'another' becomes 'a' (this could be a standard abbreviation I've not previously seen).
'european' becomes 'Pole' (someone from Poland).
'a'+'pole'='apole'
'non' placed around 'apole' is 'NAPOLEON'.
Can you help me to learn more?
(Other definitions for napoleon that I've seen before include "In France, former sovereign" , "A pig farmer was chased by" , "Former French gold coin" , "French VIP" , "The familiar Bonaparte" .)