In truth, one's too scrupulous (6)
I believe the answer is:
honest
'scrupulous' is the definition.
(thesaurus)
'in truth one's too' is the wordplay.
'in' indicates the answer is hidden within the clue.
'HONEST' is hidden in the letters of 'truth ones too'.
(Other definitions for honest that I've seen before include "Genuine; fair" , "Honourable, true" , "Free of deceit and lies - truly!" , "Virtuous" , "Genuine and trustworthy" .)