Think up (6)
I believe the answer is:
invent
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">think up</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that invent is a kind of the think up)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for invent that I've seen before include "Design for the first time" , "Be the first person to make something" , "Create like Edison" , "Originate" , "Make up (something false)" .)