Use your brain (5)
I believe the answer is:
think
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">use your brain</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for think that I've seen before include "Believe" , "Ponder" , "Meditate" , "Imagine" , "figure" .)