Vote against Marines standard (4)
I believe the answer is:
norm
'standard' is the definition.
(norm is a kind of standard)
'vote against marines' is the wordplay.
I cannot really understand how this works, but
'against' could be 'no' and 'no' is found within the answer.
'marines' could be 'rm' (abbreviation for 'Royal Marines') and 'rm' is found within the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for norm that I've seen before include "Mean" , "Small boy" , "Bacterium, virus, etc" , "Standard amount or customary behaviour" , "Required or acceptable standard" .)