Skeptical person (5)
I believe the answer is:
cynic
'skeptical person' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for cynic that I've seen before include "One who thinks only self-interest motivates people" , "Someone who believes the worst of others" , "One who questions the worth of anything" , "Doubting philosopher" , "Sort of Greek philosopher" .)