All bad leaders leave their mark and choose not to vote (7)
I believe the answer is:
abstain
'choose not to vote' is the definition.
(I've seen this before)
'all bad leaders leave' is the wordplay.
'leaders' says to take the initial letters.
'leave' becomes 'stain' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
The first letters of 'all bad' is 'ab'.
'ab'+'stain'='ABSTAIN'
'their mark and' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for abstain that I've seen before include "Go without" , "Cut it out!" , "Take no part" , "Choose not to vote, or drink" , "Forego,do without" .)