Fallacy nicely traps one disinclined to believe (5)
I believe the answer is:
cynic
'one disinclined to believe' is the definition.
I can't tell whether this definition defines the answer.
'fallacy nicely traps' is the wordplay.
'traps' says the answer is hidden in the clue (the answer is 'trapped' somewhere in the clue).
'CYNIC' is hidden within 'fallacy nicely'.
Can you help me to learn more?
(Other definitions for cynic that I've seen before include "One who thinks people are motivated by self-interest" , "One who knows the cost of everything and the value of nothing" , "One dismissive of human motives" , "One believing the worst" , "One who believes people's motives are always selfish" .)