Without success (6)
(Other definitions for vainly that I've seen before include "How conceited people might act" , "Without success, ineffectually" , "To no avail" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">without success</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for in vain that I've seen before include "Without success or result" , "Uselessly, to no avail" , "Fruitlessly" , "Without effect" , "Uselessly, without any progress" .)