A voting system one left for a month (5)
I believe the answer is:
april
'month' is the definition.
(April is an example)
'a voting system one left for a' is the wordplay.
'a voting system' becomes 'pr' (I've seen this in other clues).
'one' becomes 'li' (I've seen this in other clues**).
'left' says the letters should be written backwards.
'for' says to put letters next to each other (I've seen this in other clues).
'li' written backwards gives 'il'.
'pr'+'il'='pril'
'pril' put after 'a' is 'APRIL'.
(Other definitions for april that I've seen before include "Springtime rain" , "Start of the financial year" , "on her first kid" , "Month that's autumnal in Oz" , "Calendar month" .)