Activity of buying and selling (8)
I believe the answer is:
commerce
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">activity of buying and selling</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 commerce that I've seen before include "Business dealings" , "Sales and purchases of goods and services" , "The buying and selling of commodities and services" , "Trading activity" , "Activity of buying and selling" .)