Great achievement (4)
I believe the answer is:
feat
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">great achievement</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for feat that I've seen before include "Notable achievement" , "Exploit; achievement" , "Courageous act" , "Notable act" , "An accomplishment of fate" .)