Doubters (6)
'doubters' is the definition.
('skeptic' can be a synonym of 'doubter')
This is all the clue.
(Other definitions for cynics that I've seen before include "Disillusioned people given to disbelieving" , "They take a pessimistic view of human goodness" , "They are hard to convince, sceptical people" , "Philosophers" , "They know the price of everything and the value of nothing according to Wilde" .)