Two-thirds of the men prosecute, as will be consequential (5)
I believe the answer is:
ensue
'will be consequential' is the definition.
I can't judge whether this defines the answer.
'two-thirds of the men prosecute' is the wordplay.
'two-thirds of the men' becomes 'en' (I can't explain this - if you can you should give a lot more credence to this answer).
'prosecute' becomes 'sue' (I've seen this in another clue).
'en'+'sue'='ENSUE'
'as' acts as a link.
Can you help me to learn more?
(Other definitions for ensue that I've seen before include "Come next" , "Arise" , "Befall" , "Happen or come about as consequence" , "Follow as a consequence" .)