Assume as an axiom (5)
I believe the answer is:
posit
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">assume as an axiom</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for posit that I've seen before include "given proposition" , "Put forward as true" , "Lay down or assume (as the basis for an argument)" , "Put forward (an idea)" , "state" .)