Most high (7)
I believe the answer is:
tallest
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">most high</span>' is the definition.<br/ ><span class="explanation-format__explanation">('tall' can be similar in meaning to 'high')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for tallest that I've seen before include "most exaggerated" , "Of greatest vertical extent" , "Of extreme height" , "Most incredible" , "Most lofty" .)