Broadest (6)
I believe the answer is:
widest
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">broadest</span>' is the definition.<br/ ><span class="explanation-format__explanation">('wide' can be a synonym of 'broad')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for widest that I've seen before include "most spacious" , "spread maximally" , "most off target" , "showing maximal gap between sides" , "least slim" .)