Scepticism (5)
I believe the answer is:
doubt
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">scepticism</span>' is the definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for doubt that I've seen before include "Suspicion" , "Distrust" , "Misgiving" , "Have reservations or be uncertain about" , "Feeling of uncertainty about something" .)