Part of a royal flush
I believe the answer is:
ten
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">part of a royal flush</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for ten that I've seen before include "Five times two" , "Cardinal number" , "honour" , "No of sides of a decagon" , "PM's address, Downing St" .)