Infernal (7)
I believe the answer is:
hellish
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">infernal</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for hellish that I've seen before include "Infernally unpleasant?" , "Diabolical, infernal" , "Extremely unpleasant" , "Very difficult" , "Very much" .)