Plumb (7)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">plumb</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for utterly that I've seen before include "Completly and without qualification" , "Completely and without qualification" , "Absolutely and completely" , "'All is changed, changed . . .' (Yeats)" , "Thoroughly, wholly" .)