By what means? (3)
I believe the answer is:
how
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">by what means?</span>' is the definition.<br/ ><span class="explanation-format__explanation">('how' can be a synonym of 'by what means')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for how that I've seen before include "In what way?" , "See 16" , "Who (anag.)" , "In what manner or method?" , "By what means?" .)