Think logically (6)
I believe the answer is:
reason
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">think logically</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for reason that I've seen before include "Power of thought" , "Cause, justification" , "Sanity of senora" , "Motivation or cause" , "Rational motive" .)