Most profound (7)
I believe the answer is:
deepest
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">most profound</span>' is the definition.<br/ ><span class="explanation-format__explanation">('deep' can be a synonym of 'profound')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for deepest that I've seen before include "at the very bottom" , "most demanding" , "most insidious" , "hard to get, in the extreme" , "Profoundest" .)