Worthless horse (3)
I believe the answer is:
nag
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">worthless horse</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for nag that I've seen before include "Find fault" , "to get on one's back" , "its head to name the pub" , "Horse; keep scolding" , "Annoy constantly" .)