Hobnob (10)
(Other definitions for mingle that I've seen before include "Mix among others" , "Dawn song, poem" , "Join the crowd, mix in" , "Mix together" , "Mix (socially)" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">hobnob</span>' is the definition.<br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for fraternise that I've seen before include "Consort" , "sociable" , "Meet socially" , "Be friendly with" , "Trains free (anag.)" .)