Prone to dishonesty? (5)
I believe the answer is:
lying
I believe this clue is a double definition.
'prone' is the first definition.
(I've seen this before)
'to dishonesty?' is the second definition.
(lying is being dishonest)
(Other definitions for lying that I've seen before include "Prone - untruthful" , "Prone - mendacity" , "Prone (to fabrications?)" , "Deviating from truth" , "Resting horizontally; fibbing" .)