Arithmetical value (6)
I believe the answer is:
number
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">arithmetical value</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 number that I've seen before include "(Symbol for) quantity" , "Count, musical item" , "One may be irrational or negative" , "Dance" , "For example, one" .)