Most difficult (7)
I believe the answer is:
hardest
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">most difficult</span>' is the definition.<br/ ><span class="explanation-format__explanation">('hard' can be a synonym of 'difficult')</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for hardest that I've seen before include "Trashed (anag) - most oppressive" , "Most difficult or firm" , "Red hats (anag.)" , "most difficult to unravel" .)