Boffin (7)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">boffin</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 egghead that I've seen before include "Expert" , "Intellectual, studious academic" , "may take a bashing at the breakfast table" , "Very clever person" , "Brainy type" .)
(Other definitions for brainbox that I've seen before include "Skull - clever clogs" , "Einstein?" , "cranium" , "quiz champion?" , "Clever type" .)