Means of voting after Scotland raised tax (6,6)
I believe the answer is:
postal ballot
'means of voting' is the definition.
(a postal ballot is a way of casting a vote)
'after scotland raised tax' is the wordplay.
'after' becomes 'post' (prefix meaning after, eg post-war).
'scotland' becomes 'Alba' (Gaelic name for Scotland).
'raised' shows that the letters should be reversed in order (going up in a down clue).
'tax' becomes 'toll' (I've seen this in another clue).
'toll' backwards is 'llot'.
'post'+'alba'+'llot'='POSTAL BALLOT'
(Other definitions for postal ballot that I've seen before include "Form of election" , "Voting method" .)