Hellish (8)
I believe the answer is:
infernal
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">hellish</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that hellish can be written as infernal)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for infernal that I've seen before include "Of hell, or tiresome like a nuisance" , "Extremely annoying" , "Relating to the underworld" , "Hellish - damned" , "To do with hell, or informally detestable" .)