Less shallow (6)
I believe the answer is:
deeper
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">less shallow</span>' is the definition.<br/ ><span class="explanation-format__explanation">('deep' can be the opposite of 'shallow' so perhaps 'deeper' is reasonable for 'less shallow')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for deeper that I've seen before include "Profounder" , "Lower in pitch" , "More profound or more intense" , "Wiser" , "more involved" .)