Approximate calculation (8)
I believe the answer is:
estimate
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">approximate calculation</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for estimate that I've seen before include "Form opinion of - tea times (anag)" , "Judge the approximate value" , "Assess value" , "Calculate approximately" , "Likely amount" .)