Horse’s whinny (5)
I believe the answer is:
neigh
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">horse's whinny</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for neigh that I've seen before include "Cry coming from mount" , "Whinnying sound" , "heard on the farm" , "Animal noise (expressing 3?)" , "The noise of a bay" .)