Communication between groups (7)
I believe the answer is:
liaison
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">communication between groups</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 liaison that I've seen before include "Secretive affair" , "sexual adventure" , "Naughty affair?" , "Secret love-affair" , "entanglement" .)