Worn-out horse; chop (4)
I believe the answer is:
hack
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">worn-out horse</span>' is the first definition.<br/ ><br/ >'<span class="explanation-format__original">chop</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that chop can be written as hack)</span><br/ ><br/ ></span>
(Other definitions for hack that I've seen before include "Drudge, inferior writer" , "Chop roughly - mediocre journalist" , "Writer of uninspiring stuff" , "Kick on the shins" , "try to access unauthorised data" .)