Make excessive demands on public before a vote (7)
I believe the answer is:
overtax
'make excessive demands on' is the definition.
(I've seen this before)
'public before a vote' is the wordplay.
'public' becomes 'overt' ('overt' is associated in meaning with 'public').
'before' means one lot of letters go next to another.
'vote' becomes 'x' (how votes are marked).
'overt'+'a'+'x'='OVERTAX'
(Other definitions for overtax that I've seen before include "Put too great a strain on, as Revenue Commissioners do" , "Press too hard" , "Place too great a burden on, as Revenue officials do" , "Require too much" , "Put too much pressure on, like Revenue Commissioners" .)