Harmony in opinion (9)
I believe the answer is:
agreement
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">harmony in opinion</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 agreement that I've seen before include "Harmony, concurrence" , "legal contract maybe" , "deal" , "Harmony or treaty" , "concert" .)