Workers' organisation (5)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">workers' organisation</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 union that I've seen before include "Marriage; pipe joint" , "Coupling, merger" , "Association - guild" , "(Pipe) coupling" , "Wedding, say" .)
(Other definitions for trade union that I've seen before include "Equity is one such" , "Equity perhaps" , "Organised Labour" .)