Add up to, total (6)
I believe the answer is:
number
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">add up to</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >'<span class="explanation-format__original">total</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that total is a kind of number)</span><br/ ><br/ ></span>
(Other definitions for number that I've seen before include "Mathematical unit" , "less sensitive" , "Count - a digit?" , "Comparatively torpid" , "theme tune?" .)