Great deed (4)
I believe the answer is:
feat
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">great deed</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 "Deed; achievement" , "Achievement needing skill, strength, etc." , "Achievement needing great courage or skill" , "Notable achievement" , "Significant achievement" .)