Worked hard to convert voters (6)
I believe the answer is:
strove
'worked hard' is the definition.
(I've seen this in another clue)
'convert voters' is the wordplay.
'convert' is an anagram indicator (I've seen this in other clues).
'voters' is an anagram of 'STROVE'.
'to' acts as a link.
(Other definitions for strove that I've seen before include "Voters (anag) - made every effort" , "Endeavoured" , "Tried hard for voters" , "Made great efforts" , "Struggled" .)