Affecting vet or elector (5)
I believe the answer is:
voter
'elector' is the definition.
(I know that elector can be written as voter)
'affecting vet or' is the wordplay.
'affecting' is an anagram indicator.
'vet'+'or'='vetor'
'vetor' with letters rearranged gives 'VOTER'.
(Other definitions for voter that I've seen before include "Lively dances (esp. Irish)" , "Overt (anag)" , "One of the selectors" , "Elector" , "Election participant" .)