In base ten (7)
I believe the answer is:
decimal
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">in base ten</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for decimal that I've seen before include "A point in maths" , "Sort of coinage" , "of Number Ten" , "Based on the number 10" , "(System) based on tens" .)