Honest? Nope, phoney! (4)
I believe the answer is:
open
'honest?' is the definition.
('open' can be similar in meaning to 'honest')
'nope phoney' is the wordplay.
'phoney' indicates an anagram.
'nope' with letters rearranged gives 'OPEN'.
(Other definitions for open that I've seen before include "Candid and undisguised" , "sporting competition" , "Exposed; free" , "Start - frank" , "Candid or unlocked" .)