Spur disc (5)
I believe the answer is:
rowel
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">spur disc</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 rowel that I've seen before include "Spur's spiked wheel" , "sort of wheel" , "piece on Spurs" , "Part of a spur" , "Goad" .)