Early calculator (6)
I believe the answer is:
abacus
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">early calculator</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for abacus that I've seen before include "Counting device" , "An old counting frame with beads" , "Old counting-frame" , "Counting machine" , "that one can count on" .)