Common currency (4)
I believe the answer is:
euro
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">common currency</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 euro that I've seen before include "Continental currency" , "The Vatican's currency" , "French monetary unit" , "Currency of Germany" , "Common currency unit" .)