Integers (6)
I believe the answer is:
digits
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">integers</span>' is the definition.<br/ ><span class="explanation-format__explanation">(digit is a kind of integer)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for digits that I've seen before include "Numbers 0 to 9" , "One to nine" , "Fingers, toes and numbers" .)