Sound of amazement (3)
I believe the answer is:
ooh
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sound of amazement</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for ooh that I've seen before include "Expression of surprise" , "Exclamation of delight" , "sound excited" , "Exclamation of surprise or pain" , "My goodness!" .)