Infuriating (12)
I believe the answer is:
exasperating
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">infuriating</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for exasperating that I've seen before include "Extremely annoying" , "Irksome" , "Very frustrating" , "Infuriating" .)