Harmonium (5)
I believe the answer is:
organ
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">harmonium</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for organ that I've seen before include "Church keyboard instrument" , "With prompt enthusiasm" , "What makes use of full stops" , "periodical" , "colon?" .)