Second vote choice (9)
I believe the answer is:
selection
'choice' is the definition.
('selection' can be a synonym of 'choice')
'second vote' is the wordplay.
'second' becomes 's' (common abbreviation).
'vote' becomes 'election' (election is a kind of vote).
's'+'election'='SELECTION'
(Other definitions for selection that I've seen before include "Act of choosing" , "Horse tipped for betting" , "Choice, pick" .)