Gained knowledge (6)
I believe the answer is:
learnt
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">gained knowledge</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 learnt that I've seen before include "Studied" , "Found out" , "Picked up" , "Heard" , "Committed to memory" .)