Reportedly vote against animal noise (5)
I believe the answer is:
neigh
'animal noise' is the definition.
(sound of a horse)
'reportedly vote against' is the wordplay.
'reportedly' shows a homophone (sound like).
'vote against' becomes 'nay' (I've seen this in another clue).
'nay' is a homophone of 'NEIGH'.
(Other definitions for neigh that I've seen before include "Comment from stallion" , "Mare's cry, e.g." , "Whinnying sound" , "Horse's whinny" , "Beastly sound" .)