Pick leader in secret ballot (9)
I believe the answer is:
selection
'pick' is the definition.
('selection' can be a synonym of 'pick')
'leader in secret ballot' is the wordplay.
'leader in' indicates taking the first letters.
'ballot' becomes 'election' (I've seen this before).
The first letter of 'secret' is 's'.
's'+'election'='SELECTION'
(Other definitions for selection that I've seen before include "Act of choosing" , "Choice, pick" , "Horse tipped for betting" .)